Does the bond weaken if you have your companion attack? I figured it'd be good for the bond since Elanthia is full of sociopaths who go around killing everything they can, but someone told me that our companions don't like it.

No, it has no effect, unless you tell your companion to attack you, which will.

~ Nuadjha, the Briar Fox

You inhale deeply upon your pipe, puckering your lips as you send out three rings of smoke before you, then puff out a small vine of smoke that darts right through all three which causes them to disperse in a hazy shroud!

As I know it there are only about 3 or 4 things that can weaken your bond, attack or cast any kind of spell at your companion it has to ward even 102, ask your companion to attack you as it will think your weak an mentally unstable for doing so, leave your companion injured and not offer it aid for extended time or let it die, (although it doesnt really die just drags itself off out of sight for a few days)and completely ignore it, which I dont know if that actually hurts, but it definitely stops improving the bond.

Possibly.. get it arrested or banned from a town by forcing it to break a law, not sure on that one.( I havn't seen that happen in a very long time, but it has happened). I remember someone years ago who would always have his Mastiff attack thieves as part of his R/p if he spotted a thief. That didn't last long till the companion was drug outa town and banned. I personally thought it was a pretty cool R/P idea, the Constable wondered if it had Rabies and threw it out the gate, and locked up the ranger in jail.