The users who upload copies from other users are showing little respect towards the rest of us.
The users who copy worksheets from other sites are showing little respect towards the authors of those websites and towards the users who spend hours creating wonderful original worksheets and share them with us.
If the word "copy" hurts them, the solution is very easy: don �t copy.
But, on the other hand, I agree that we should be careful with the words that we use, because sometimes there are errors. For example, when someone uploads the same worksheet in two different websites, and we think it is a copy. Imagine that you are trying to contribute to a website and the feedback you get are the words "thief", "shame", "stolen"...
It happens once or twice a month that someone is wrongly accused. It is not much, but I think it is reason enough to avoid those words.