The poem If by Rudyard Kipling provides a cynical view of the world as it gives advice on how to overcome the treacherous world.  Although the poem views the world in a bitter light, Kipling offers hope.  By understanding the dangers that lay ahead in the world it is easier to prepare to overcome the obstacles.

Kipling's cynicism is seen throughout each stanza.  In the opening lines he states people will lose their heads and blame it on you.  He is implying people will make mistakes or poor choices and blame their misfortunes on you.  He goes on to claim people will lie, hate, twist your words and try to hurt you.  Further, Kipling refers to the finite nature of time as the "unforgiving minute" which demonstrates his adversarial approach to the world.

Despite the bitter characteristics Kipling gives the world, the poem is also about hope.  The hope to conquer the world by understanding it is not always a nice place.  He provides a pep talk when he challenges you to hold on when you think you having nothing left "Except the Will which says to them: 'Hold on!'".  In closing Kipling notes that anyone who heeds his advice will conquer the world.

How does the poem "If—" reflect Kipling's bitter vision of the world?

This is a really interesting question.  I have always viewed the poem as a very positive one, a father imparting words of wisdom to his son.  I never looked at it that there is a bitterness present in how the father must advise against all of the potential for evil and temptation in the world.  This would be why he has to advise him in the way that he does, for so many others have failed to heed such words of wisdom.  If this is true, then there is a great deal of bitterness present because so many others have demonstrated the opposite of the words the father speaks.  Making the assumption that this is true and that the speaker and Kipling are one in the same, the bitterness present is that there have been so many opportunities for young boys to prove they are worthy of being "men," but have failed in the process.  The father's advice is necessitated, then, because of fear that his own son will wind up like others.  Perhaps, another layer of bitterness could be extracted if we make the argument that the father was one of these failures, meaning that he speaks from the voice of experience, the one that could not live up to the same ideals he wishes for his son. In a desperate attempt to not relive his own sins on his son, the poem emerges.

I think that you can say Kipling has a bitter vision of the world because of the kinds of things that he is warning "his son" about.  If you look at everything he says to his son, he is painting a picture of a pretty negative world.  He is telling his son about all the bad things he will have to deal with.

For example, he tells his son that everything will fall apart and go wrong.  Not only that, but when it does, people will blame him (the son) for it.  He tells the son that he will work hard to build things up and then other, lesser, people will come and tear them down.  He, the son, will have to deal with this sort of thing.

This seems to me to show that Kipling had a bitter outlook -- that he thought that things tend to go wrong and that people tend to act badly.