Don't we all have moments in our lives where we're tempted to say we've been far too "good", where's it gotten us, we may as well join the bad guys and get in on the action? That's where Tim was after being framed and driven out of town with no justice. He'd just spent forever being straight-laced and "good", holding every sarcastic remark in for years, at the school, putting up with it all... tension building.... then
Trask frames him for murder.
I think any of us would be tempted to throw away the moral rule book at that point. It's one thing to plot and plan over months to do a bad thing though, and actually do it. When the time came, I doubt Tim would act. Beth tried to go to the dark side, and she couldn't. It's a common reaction to sudden disillusionment, then we snap out of it when we realize we really do believe in our principles after all.
I know that about Tim all through this, so I never think badly of him.
Welcome back my children, you big old scary Halloween emoticons were missed. Some are missing though. The skull with the wig for one.