You can tell the diff to ignore spacing with an option. It still ends up messing up stuff like git-blame and other stuff and isn't always worth it.
The big problem with OP's point of view, IMO, is that you change the authorship of the lines when you line things up like that. If it is done from day 1, fine. Otherwise leave other people's code alone.
Why? Because unless you are using a system that makes blame slow (I'm looking at you, git), blame your goto helper for understanding the code's evolution. Our blame is essentially instant and I use it to debug problem reports while I'm on the phone with the customer all the time.
I'm all for good style guides and obeying them. But rewriting other people's code for you shiny new style hides a lot of useful history.