Going back to the beginning of the discussion, MacGyver got to the point where violence was the only available option in most episodes, but although he often had to end a conflict with violence it was rarely him who started it.
Also, he always tried to use the minimum amount of violence possible to finish a fight and on the few occasions where his actions resulted in a death, the regret on his face is clear to see. I'm thinking particularly of Log Jam here.

For me at least, swinging the first punch doesn't count as starting it if the person you're swinging it at has already done something violent and/or thoroughly despicable that's put innocent people in danger

Opinions may vary, of course

But that's the whole point. Swinging the first punch is the point at which he's resorted to physical violence.

It doesn't matter what a person has done. If you throw the first punch your making the decision to use violence to resolve the situation.

I think in a lot of situations violence was his only resort more than his last resort. There's quite a few episodes where he doesn't seem to explore any other options other than to blow something up, knock someone out, etc and I think that is largely because the situation he is in is a him or me type situation. If he doesn't stop the bad guys quickly they will stop him "permanently".

Having said that though, he did always try for non-lethal as much as possible, even though there does appear to be a couple of times at least where the option did turn out to be lethal.