I agree. Never assume an opponent is ever anything but a hardcore serious threat that knows how to hand you your ass it you go at it anything less than hardcore yourself. Take them out as rapidly and violently as possible.
Chances are that mugger as been in lots of fights. I am troubled about your assumption that if you come across some stupid fight or if a mugger attacks you he or she does not have skill or is easier to beat. These sort of assumptions are dangerous things to make. As I am find of saying, when it is time to play "I bet my ass" I am playing for the whole thing and I am going to fight my opponent, any opponent like he is skilled and dangerous. But I was a supervisor in a psych crisis center and I've seen my staff getting schooled because they didn't think that a suicidal 15 year old girl was a threat. I don't post here that often but this one needed saying.