The only reason I didn't think it was the right time is because Toews is the one that committed a penalty (cross-checked him) then fought him (instigator)... why didn't he just jump all over Thornton immediately after getting punched in the back of the head like many are claiming that is the reason Toews was fired up? Why did he go out there and hack around for a minute or two? That's the only problem I had with it. If he wants to retaliate on a cheap shot, or defend himself, that's fine but taking a double minor and chasing Thornton around just made it look worse than it could have been.
You're right though, without being on the ice it's easy to judge, but that's just the way I saw it. I don't think it's wrong for Toews to fight, I just thought the timing was off. If he would have jumped Thornton off the bat he never gets the cross-checking penalty, maybe he still gets the instigator though, or maybe not depending on what the refs see.