Yes, you can 'boycott' a cel dealership.  Or at
least, I've found it not so hard.  Of course, I'm
not 'boycotting' any of the major dealers, I have
no reason to.  However, there are some people I
won't buy from.  I've passed up some cels I really
wanted, even some wishlist cels, because I didn't
want to deal with the sellers.  I thought to
myself "Every time I look at this cel, I'm not
going to think about how great this
scene/character/cel is, I'm going to think about
how I had to work with someone I found slimey in
order to get it.  I would not enjoy this cel if I
were to buy it."  I don't like to make a big deal
of it or name names because that's just likely to
lead to a flame war, but I'm tired of reading the
false claims that people are all desperate like
that and there's no way to avoid it.  Maybe some
people are, but I'm not one of them.  I firmly
believe that if you wait around, a nicer, cheaper
different cel that you want more will come along. 
Maybe that's just because I want _a lot_ of
different cels ^_~

Keys
Uh... I updated my gallery a few days ago or
something, planning to update again soon...