It's unreasonable your bf is trying to force you to engage this person rather than simply be cordial.

I have only seen this type of force in two scenarios

1. Guy friend is a pos and the gf not wanting to hang out with him makes the bf feel guilty about what a pos his friend is. The bf can overlook the pos traits because the guy friend is good at X game or childhood friends but when his gf doesn't hang out with him then he feels guilty that his excuses aren't enough to overlook the pos traits.

2. Girl friend who is gay/bi and is very very touchy and does provocative stuff. The bf often has a crush on the girl friend and wants his gf to befriend her in hopes they will do girl on girl OR he gets a threesome.