On a serious note, I will say that some good morals/ethics/behaviors do indirectly enhance ones ability to achieve skill as a fighter/martial artist.
Reason is that most criminals are inherently lazy, have a host of psychological problems, or both.
People who try to make money off of crime are usually inherently lazy. If they weren't, then they wouldn't be trying to take shortcuts and would instead try to work hard and get a legit job like everyone else. Well, one thing that is nearly impossible to do is to become seriously skilled at fighting without working for it. Martial Artist who are skilled generally have to train hard to get there. Most criminals who do crime for $$ aren't guys who just left the boxing gym and are looking for random training opportunities (RTO's) on the street. Most criminals are looking for victims, and the easiest way to achieve their goals. Training hard is not really an easy way.
Other criminals who are not in it for the money, such as violent criminals who assault others frequently, have anger problems that cause criminal behavior, etc., usually have major psychological issues. In order to train hard and seriously, one has to possess a degree of patience, perserverance, humility (enough to be able to recognize mistakes for self improvement), a drive to better oneself, and a degree of positive thinking and self-worth. Someone with violent criminal tendencies and behaviors are usually lacking in one or more of these areas.
That all said, I am a pesamist when it comes to the skill levels of the average martial artist. I think that the average violent criminal would and could take the average martial artist in a fight. Most average martial artists took up "martial arts" in part because they are also lacking in one or more of the qualities that it would take to acheive a really high level of skill; except they lacking these qualities for different reasons - and that is because they are usually on the physically/mentally weaker side of society and they want to make improvements in those areas. This is why your more likely to hear, "I want to get in shape" or "I want to build self confidence" as viable reasons for taking a martial art over "I want to be a better fighter". The average criminal has been training through experience to monopolize on other peoples weaknesses, where as the average martial artist has not overcome their weaknesses enough to not get taken advantage of by the average criminal. So out of pure aggressiveness, violence, and ability to monopolize on the weaknesses of others, the average preditory criminal would be able to take the average martial artist.
That all said, if we are talking about the above average martial artist or even the extremely skilled martial artist, I would vote for the extremely skilled martial artist. The extremely skilled martial artist, in my opinion, IS also an extremely skilled fighter, and will be able to take care of most violent criminals (recognizing of course that no one is 100% safe, and that anyone could get killed regardless of skill). And, I would have to say that due to the nature of what it takes to achieve this high level of skill, I would say that most violent criminals do not possess the qualities to get there.
Paul