Is winning on time bad manners? No
Claiming that the opponent should have resigned because they themselves did not have enough time left on their clock to finish the game.. That my friend, is bad manners! If someone doesn't have enough time to deliver checkmate in an otherwise won position. It is entirely their own fault.
just get over the idea that it is ever bad manners to win on time...time is part of the game and must be managed, just like every other piece...
That is a very good point. I also think that it is perfectly fair to win on time.
At higher level chess this is even unpolite to continue play in a totally lost position - giving respect to the opponent means believing he is able to launch checkmate. So playing only on time is considered a very bad habit at master and higher level - but I mean playing on time in a lost position or a dead draw! In a "normal" position it is fair.
However, in amateur games it is normal to play till checkmate or "bare kings" and playing on time should be considered just another form of implementing this idea. If you require your opponent to show that he knows how to checkmate it is ok to require him do so quickly.
So, an average member of chess.com should not feel guilty for playing on time even at 2 moves before mate - and noone should feel guilty when the position is still full of play (not a dead theoretical draw)