Just like in real life, sometimes you (unintentionally) do something that irritates other people. Most of the time, they complain once and go on with their life. But a small percentage of them wants revenge. And on SO and sister sites, downvoting and question closing can be used as revenge. But this mechanism isn't very effective. First every down vote cost only 2 rep and the revenger loses 1. Second the system detects if person A downvotes person B a lot and takes measures against it. Multiple accounts are also detectabele so the system is rather fair.
I can advice you to ignore the downvotes, or to send a mail to the team. Because public complaints can backfire.
In the end we just want a great resource for programmers.