That's oversimplifying the argument. A person who functions in the realm of politics you can give a chance. A person who is working outside, you can't.
A person who is reversing social progress, especially for minorities, won't be given a chance by anyone on the left. Nor do they have to. There is no obligation on them to say, "Oh well, he just called Mexicans rapists, but let's give him a chance.".
Lastly, he has already done enough during his lifetime, during his campaigning and now in his first two weeks to show what's he's like, and what is to be expected from him. So he had his chance, and he blew it.