Nooh was the second father of all mankind, and the first of the Messengers (Rusul) to the people of the Earth. This great Prophet lived a very long life: he called his people for nine hundred and fifty years to the tawheed of Allaah and to making all worship purely for Him. He did not become weary of this, nor lose interest. He called them night and day, in private and in the open. Allaah, the Most High, says,
"Indeed We sent Nooh as a Messenger to his people ordering him to warn his people before a painful punishment should come to them. He said, 'O my People, I am a plain and clear warner to you, that you should worship Allaah alone, avoid disobedience to Him and obey me. If you do so He will forgive you your sins and grant you respite until an appointed term. Indeed when the term decreed by Allaah comes it cannot be delayed, and if you knew you would submit to and obey your Lord.' Nooh said, 'O my Lord, I have called my people day and night to worship You alone and warned them of Your punishment but my calling them to the truth only results in them turning away from it.  Whenever I call them to worship You alone and to obey You, and to dissasociate themselves from the worship of everything but You, so that You may forgive them, they thrust their fingers in their ears and cover themselves up with their garments, so as not to hear. Then they persist in their disbelief and arrogantly and obstinately refuse to follow and submit to the truth. Then I called them loudly and openly, and I called them individually and privately. I said to them, 'Ask your Lord to forgive your sins and repent to your Lord from your unbelief and association of others in worship with Him, and make your worship sincerely and purely for Him, then He will forgive you, indeed He greatly forgives those who turn to Him in repentance and seek His forgiveness. He will then send you rain in abundance, and grant you increase in wealth and children, and provide you with gardens and rivers. What is wrong with you that you do not have awe and fear of Allaah, when it is He that created you in successive stages? Do you not see how Allaah has created the seven heavens one above the other, and has placed the moon therein as a light and has made the sun a lamp? Allaah it is who created you and brought you from the earth, and He it is who will return you to it, and then resurrect you from it. Allaah - it is Who spread out the earth for you, so that you may travel about upon wide roads.'' Nooh said, 'O my Lord, they have rejected my call and opposed it, and have instead followed the call of those whose wealth and children only increase them in error and take them further away from their Lord. Furthermore the leaders have plotted a mighty plot, and they have said, "Do not abandon your gods. Do not abandon Wadd, nor Suwaa, nor Yaghooth, nor Ya'ooq, nor Nasr." Indeed many have gone astray due to the idols. O Allaah, grant no increase to the transgressors except in error.  Due to their sins they were drowned in the Flood and entered into the Fire, and they could find no one to save them from Allaah's punishment." 
So what did the da'wah of this noble Messenger comprise of, and Allaah has told us the summary of his noble da'wah which continued for nine hundred and fifty years?! Indeed it was an earnest and painstaking call to the tawheed of Allaah and to make all worship purely for Him. It was a tireless effort and he used every possible means available to him to convince them of his call. He called them privately and individually, and he called them openly. He encouraged them and warned them, informing them of the promise of good for the obedient, and evil for the disobedient. He gave them practical and intellectual proofs, from themselves and their lives, and what they saw before them with regards to the heavens and the earth, and the clear signs and lessons contained in them. All of this failed to benefit them and did not cause them to accept. Rather they persisted in their disbelief and error, and they rejected all this obstinately and arrogantly. They persisted in their adherence to the idols and false and futile objects of worship. So the result of this persistence and obstinancy was destruction and annihilation in this world, and everlasting torment in the Hell-fire in the Hereafter.
At this point we may ask: why did this great Prophet continue for such an extremely long period of time, expending huge efforts, untiringly and without languidness, calling to the starting point of tawheed?! Why did Allaah praise him so highly, and cause him to be remembered, and make him one of those Messengers who were the firmest of all in their determination (oolul-'adhm)? Does the call to tawheed deserve all this esteem? Is this methodology an establishment of this procedure for this noble Prophet in opposition to logic, wisdom and intellect? Or is it pure and certain wisdom, and what is demanded by correct logic and sound and perceptive intellect? Why did Allaah approve of following this methodology in da'wah for 950 years, and commend him, and cause his name and his story to endure, and impose it as a duty upon the greatest of the Messengers and the one having the greatest intellect of all the people, that he should take him as an example to follow in his da'wah and his perseverance?
The just answer, established upon intellect and wisdom, and upon understanding the status and position of Prophet hood, and having the greatest trust in it and giving it its due respect, is that the call to tawheed and striving to wipe out shirk and to purify the earth from it, does indeed deserve all of this. It is indeed wisdom itself and is demanded by natural inclination and intellect. It is furthermore, a binding obligation upon every caller to Allaah that they understand this methodology, this great and divinely inspired da'wah and great goal, and that they devote all their effort and energy to its attainment and its being propogated throughout all of Allaah's earth. Furthermore that they work together, cooperate and unite, and sincerely attest to each others' truthfulness. Just as the Messengers, the callers to tawheed, were: the earlier ones telling of the coming of the later ones and the later ones attesting to the truthfulness of the previous ones and promoting their call, and following the same way. It is also binding upon us to believe that if there was any other methodology better and more correct than this methodology, that Allaah would have chosen that for His Messengers and would have favoured them with it. So is it fitting for any Believer to turn away from it and choose a different methodology for himself, and to arrogantly seek to attack this divinely laid down methodolgy and its callers?!
 At-Tabaree reports from Qataadah, "It has reached us that a man would take his son to Nooh and say to his son, 'Beware of this man, don't let him lead you astray, for I remember when I was your age, my father brought me to him and warned me against him just as I am warning you.'"
This supplication of Nooh against them came after he was informed by Allaah that they were not going to be Believers, as explained by al-Baghawee.
 Soorah Nooh (71):1-24.