Here's what I think:

1. Just tell your drummer what you think of the other guy. If he's a good guy, he'll understand and things can be worked out from there. If not, fight fire with fire. Invite some dude with bagpipes over to jam and see how your drummer likes that...... :)

2. I don't see this as an excuse for not playing at all. This would make me want to play more. Pick up your guitar and just play anything at all. Hold down all the strings and just slam out a muted rhythm if you want. That's all I ever seem to do..........
That's probably not the answer you're looking for, but I would seriously just write a song about it. What you described would probably make an alright song, as long as it wasn't some sort of "my heart/hurts bad/you've made/me sad" crap.