A terrorist is just a freedom fighter by another name. Whether he counts as a hero or a villain depends entirely on your point of view.
Yeah. The thing is about guerrilla warfare is that the gray area is pretty difficult. It's easy to label purely civilian targets as terrorism but it's hard for people who have military targets blown up to NOT call it terrorism. In RL, we still label the military housing and Pentagon attacks as terrorism and rightly so. Because we're angry and not inclined to be forgiving to those who murdered friends and loved ones.
But even if we were so forgiving, the line is nebulous. Let's say Gul Dukat is having a Klingon coffee at Quarks and a Bajoran resistance group blows it up, killing 30 people but taking out Gul Dukat and his guards. Is that terrorism? What about blowing up Cardassian settlements on Bajor? If occupation and settlement is the goal, what about making that difficult. What about a weapons factory? The United States entered WW1 for blowing up the Lusitania despite the fact that it was ferrying weapons. Everyone in the USA was outraged, however, by the attack because of the heavy civilian deaths.
War, itself, is fundamentally terrorist because its predicated on forcing one side to be afraid of the other to the point of submission.
Still, that doesn't mean there's not some real scumbags out there and that "everything goes" either. Morality is slippery that way.
Yes, he was convicted and serving time for the crime of being associated with the Maquis. There's no question he was a criminal. How bad was he, though? Was Paris on a mission to terrorize civilians, or attack legitimate military targets? Did he even accomplish his mission, or was he prevented from doing so by his capture?
I think the writing works better for Locarno, actually. Having been expelled from Starfleet academy, he's ruined his chances of being a Captain and basically feels the Marquis is the place that he can find his own form of redemption/fame and glory. Imagine the irony that it turns out he's rotten at being a freedom fighter, too.