Honestly, as much as I find it highly inconsiderate to park in multiple spots, it has never occurred to me to “do anything to their car.” If I could, I would move it over so that I (or someone else) could park in one of the spots.
As far as the point that was made that “you never know what’s going on with the other guy,” this logic works for an extraordinary situation. Unfortunately, I see the same cars parked in an inconsiderate manner very often. I do not believe that these people have “emergencies” or the like every time I see their car taking up two spots when I’m trying to get to night Seder.
דן לכף זכות does not mean that we should assume that the owner of the vehicle is secretly also a field medic performing emergency surgery in some undisclosed location. It just means that we should assume he doesn’t do it deliberately to bother other people, he perhaps doesn’t even realize that he did it, and if someone would tell him about it he would be more careful in the future.