I don't know, guys. I'm not a fan of Bodom either, but I would never leave a gig early unless I had to make it home in time for something. If I buy a ticket to something, I'll see it through, not be an anti-establishment rebel and leave before the headliner. So what that you've left early - the money will still be going to the band you don't like.
But uh, yeah, I'd stay for Bodom. Definitely.