I'm in the middle on this...
I'm not a BFMV fan, and think their mix of emo and metal is pretty weak.
But on the other hand, I saw them supporting Guns n Roses last summer and they actually put on a good performance.
They're one of those bands who, despite being totally wank on cd, redeem themselves with an energetic and powerful live show.
At the same time, I 100% agree with everyone saying that they don't belong on this bill.
But, instead of doing the typical Download Festival thing of throwing bottles of piss at them, why not just turn around and buy a few beers while they're on?
As for their logo being on the shirts, if anyone comments saying "You saw BFMV, you're an emo fag", tell them that you didn't want them there, you didn't watch their set and that they (the person commenting) should piss off and gut themself with a broken bottle.
Remember you're not paying 99 Euros for a BFMV ticket, but a WACKEN FESTIVAL ticket, to see amazing bands such as Immortal, Blind Guardian, Grave Digger, Rage, Sodom, etc