Altist

Someone who is alt-left / right at the same time. The polar opposite of a centrist. Someone who claims to be left or right but has the same beliefs as those they claim to be against.
Ie- being an alt leftist and claiming to be against fascism but espousing fascist beliefs

Hey man did you hear Johnny is an altist? He’s says the police have no right to stop his protest just like Dave the Nazi said about the alt right blockade!
Johnny-down with nazis! You people have to do what antifa tells you to do and think how we tell you to think!!
Donny- jeez Johnny I thought you were a leftist but clearly you’re an Altist!!!

Altistic

When someone is both in the alternative scene (be it music or clothing style), they are also on the Autistic Spectrum, as well.

"Lucien loves rock and indie music, and seems to really favour grunge."
"Yeah, he's also on the Autistic Spectrum, so those are some of his interests, too."
"Oh, so Lucien is altistic."