I don't think you've missed anything. If some people are claiming that safety pins are all about their particular minority, it's just yet another example of the way the oppressed frequently fight with each other, rather than uniting against common oppression. Or even more likely, it's just them being human - that is, self centered and unable/unwilling to see other people's points of view. It's easier to see the oppression that affects you; harder to see whatever privilege you have.