A joking objection: somebody that refuses to join due to sans serif would be harmful to the cause if they join anyway.
A serious objection: it feels wrong and dangerous to join a group that you don’t support 100% at the time of joining. This feeling is adaptively correct because group efforts often drift or get hijacked, and a group that’s a little out of tune with you is more likely to drift away over time. Especially if the group is new.
Emotions can also have a lower time preference than your conscious self. For example, a surge of anger can make you stand up against a bully and win much more than the present confrontation in long term self-respect and respect of others, even if you eventually “lose” this particular conflict. My subconscious is always tracking the intangible “social” terms of my long range utility function, and over the years I’ve come to appreciate that.