Why the hate on the Psion class?

[Max_Killjoy]

The lesson I'm getting from this is to say screw all distinction between anime, space fantasy and so on and just make the fantasy I want. and that the only thing holding anything back is making it look "right" to an outside observer. when anything looking "right" is an illusion.

I started reading that and was thinking "well, sure, if that's what you find fun and engaging, go for it", and then you got to that last part, and I want to ask why you'd crap on other people's fun as part of griping about them crapping on your fun.