So let me get this right, you are asserting that there are atheists who don't believe in certain versions of God based on the argument from the existence of evil? Well, as you say, we may have vastly different experiences with atheists, however, the formulation I most hear from many atheists is "I cannot believe in a God that would allow evil." Perhaps I just happen to experience the minority of them the majority of the time.
Only a fool, theist or atheist or whatever else, would disbelieve something based on the reason that they do not like it.
A reasonable person rejects worldviews because they don't make sense, they don't have any validity or evidence, etc. The problem of evil is not a problem for god's existence. It's a problem when it comes to the existence of an omnipotent and omnibenevolent separate, personal, deity. It's an argument against skillful and benevolent design.
Your response would pretty much confirm that you misunderstood, but lets see if I can help you along. By what would an atheist use to determine what is "evil" apart from at least a theistic basis? Also, any argument against the God of the bible presupposes a certain reading of the Judeo-Christian scriptures, would you not determine that would constitute an importing of at least some elements of the specific viewpoint? The Judeo-Christian worldview carries a commitment that the scriptures communicates a truth about God. What I most often find is that atheists must import the most fundamentalist viewpoints into their discussions about God to prop up their own straw man arguments.
"Evil" is a useful word for convenience but lacks detail. Words like "malevolent", "sadistic", "violent" and so forth are more appropriate.
Reason and other tools can be used to sort out actions that are either good/evil, skillful/not skillful, intelligent/ignorant, benevolent/malevolent, etc.
A self-absorbed, violent, wrathful, sadistic, jealous deity would fall under the category of evil for the same reason any human would.