Everyone says “a partner who respects you wouldn’t keep you from your friends”.

But I also see a lot of people say “a partner who respects your boundaries wouldn’t keep a friend if it made you uncomfortable”. 

These two statements seem contradictory to me. When does someone cut off a friend for their SO? When do they tell their SO to just accept the friendship or it’s over?

What if one party is still friends with an ex and the new partner is uncomfortable? 

What if one party has a lot of *platonic* friends of the opposite sex but their partner doesn’t want them to have ANY friends of the opposite sex? 

When is a boundary considered “reasonable” and when is a boundary considered “controlling”?