Yeah but the movie doesn’t exactly make it clear that the rebels are wrong to blow up the Death Star or that Vader is wrong to kill the Emperor.
It’s like if Han Solo had slammed the Millenium Falcon into Luke’s X-wing fighter in A new Hope to stop him from blowing up the Death Star. “Hey Luke forget this killing business let’s do some saving instead!” Sometimes you can only save what you love by killing a whole lot of people. Finn’s decisison to sacrifice himself is exactly the same. Stopping him only makes sense if it is made clear the sacrifice wouldn’t work. (Which by the way makes Finn look like a bit of an idiot.)