Hate is an interesting word in English. Conversationally, it can express many negative sentiments. For example:
I hate having to scrape the ice off my windshield in the morning!
means:
I wish I had a garage where I could park my car!
As for what you asked:
Is there a word for hating a person you don't know, but you hate because of something he did.
I agree with StoneyB; I can't think of a single word that captures this, and none of the related words I found on Wordnik offered much help.
However, we can do this in English by using a couple stock phrases. We can use "the way" (or "how") to reference the behavoir, and "that person" (or "this person") to hint that we don't know the individual. For example, we might say:
I hate the way that guy cheated off my exam.
or:
There was this student sitting next to me – I hate how she copied the answers from my test!
I think both of those reasonably capture the essence of "hating a person you don't know, because of something they did."
In English, there is an oft-used phrase: Don't hate the person, hate the action. I think my suggested sentences might lean toward that side of things: one could read them, and notice that the hate isn't necessarily directed at the people, but at the act of cheating. Still, it can be hard to disassociate an action with the people who do it. But now I'm waxing philosophic.
Best Answer
You haven't provided sufficient context to give you much of an answer beyond generic phrases like selling used or pre-owned or second-hand items.
You could be getting rid of junk you don't want. You could be selling items that some people would consider rare finds. You could be selling items that still have lots of life and use left that shouldn't go to waste.