I think the major exchange can be over-rated. As has been said, there are times when losing it is a necessary combination, and it has nothing to do with the opponent's estimate of a player's competence. Also, people shouldn't spend too much time psyching themselves out. If the opponent is swapping down to show their superiority, so enjoy the fact that you're seeing a good player at work. If they do the dance of the 6 or 7 queens, then think 'what a fool' and try to avoid playing them again.
It depends on you what you make out of it.
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If someone did a 'knightmare' for you, never report him. It's happening in online chess for fun. You can just resign if you don't want a that kind of ending. It's you, who allowed your opponent to do it. BTW, I recommend you to not to do this kind of funny things in OTB, because sometimes, the arbiters may forfeit your game for 'disrespecting the game of chess'. It happened once in a tournament, in the game of x vs y. I don't need to tell you the names and the reason. But it's a popular incident.