eh, I grew up with the mentality that everyone had to be invited and I still don't like it. I also think there is an element of entitlement in the concept that we have to invite everyone and accomidate everyone all the time. You know sometimes you just want a certain type of party that may not be appropriate or work for everyone. I encountered this problem when my dd was getting older and she wanted to do a scary halloween theme, but her BFs much much younger sibling was not going to appreciate it. And their mom just didn't get it. Apparently my dds party was supposed to revolve around her friends much younger sibling. We ended up being forced to invite him and of course he got scared and ended up going home even though we toned it down, for one kid. That my dd wasn't even really friends with. At some point enough is enough. No one is owed an invitation to anything.
Everyone is going off on this one person concept, but really it's not like the whole class but one person was invited. In reality 2 girls out of the whole class were invited. 1 girl and all the boys weren't. As a kid that was forced to invite everyone I hated it.