Whether a man is a cheater or cheating is inherent in him, well depends on his values, yes he can be a cheat and also a saint at the same time, few black sheep's cannot swamp the entire male community as inherent and perpetual cheaters, for that would be a sweeping statement.
Coming to the point, what is cheating again depends on the kind of relationship you share, a man will never cheat provided he has that kind of compassion with his/her partner, if they do not have compassion then cheating is a rule than exception.
Well whether cheating should be pardoned, again depends on the relationship and values, if you really care then no cheating is cheating for you have the magnanimity in your relationship that one stray incident is too small to even tickle rock solid relationship, i believe forgiveness is divine