First time you heard that D&D was somehow "evil."
Growing up in the 80s, it was pretty much impossible to not be aware of the somewhat sinister reputation enjoyed by Dungeons & Dragons. Hell, it was a big part of the game's appeal to most kids, I'd say, including myself. You had the double-whammy that D&D was Satanic, and that it led to insanity and/or suicide. (Imagine if the mainstream media had picked up on Call of Cthulhu!)
So I can't say when I was first aware of the game's evil reputation any more than I can recall when I was first made aware of the game itself. They went hand in hand back then.
I do recall vividly, however, that when I told my parents I wanted to "get into" D&D, my mom's jaw visibly clenched with anxiety. I actually laughed and promised her on the spot I wasn't going to kill myself.
At the time I had two sets of brothers for best friends, so I thought I'd be good to go for forming a game group, but then one of the sets moved away that summer, and the other set demurred from playing. This came as a surprise, as they had shown great interest in the back-issues of Dragon magazine I'd been purchasing. When I pressed them for a reason, they admitted it was because their mom, a pretty devout Baptist, wouldn't approve.
I never got that impression from her, though. I have to wonder if the kids were just assuming she wouldn't approve, based on the game's reputation?