Sure, too much of X is bad for you applies to just about everything. In fact the sentence is tautological, because you've already said it's "too much", which implies that it's bad for you.
The numbers of 5-8% given by the poster are truly absurd though.
How much is too much is surely complicated. It is based on your activity levels, genetics, age, state of health etc. Whatever too much protein is however, you should just naturally feel like not eating any more protein when you've had enough, and want something else like fat, right?