Originally Posted by
TouchandFeel
"Ma" in this context most certainly implies darkness in the sense of dark equating to evil/negative. The character for "ma" conveys a dark/evil spirit or force, often associated with curses in the way that a person or object can be beset or imbued with a dark spirit or force. It is not conceptually synonymous with magic as you state.
"Mahou" can be flavored good or evil because just like its closest English translation, magic or mystical/supernatural abilities, it is general and does not have an implied good/bad/light/dark affinity like "ma" does. Saying that it can easily be taken as "evil force" or "demon magic" is a big stretch.