TLDR; some fan complains that the comics depicted a troll war as a “touch football game between overweight accountants” instead of something truly gruesome and that a sex scene was “just rocks”. It’s a long rant that boils down to “your stuff is too cutesy”.
The author rebukes that nonsense because she knows she has younger readers and she doesn’t need to do that explicit sex and violence anyway.
I don’t think that was the case in 1981, though I wasn’t alive and can’t say it for myself.
Also, the trolls, as far as shown in the comics up to the point the reader mentioned, weren’t fascists. Isolationists, greedy, cheating, cowards and distrusting of non-trolls (aka xenophobes). Calling them fascists from that is one hell of a leap, no wonder the author snapped at that with “look it up on a dictionary”.