> I don't know how many times I could not commit my code because I left a space at the end of a line, or an empty line contained whitespace

Trailing whitespace causes issues with git, editors, diff tools, and numerous other things, as well; keeping it out of a repository is a good thing.

> I had only one blank line between two class definitions

I certainly agree that that's the kind of thing a tool should help with rather than complain about and make you fix.