Yes, the old testament has some ethically bad things in it, all Abrahamic religions share that. I’m also atheist. I just don’t make a point of commenting “fictional character” on a meme that happens to use the word “god”, not even capitalized lmao. Perhaps you aren’t aware of how much of a militant atheist you come off as. Out of curiosity, have you ever put the bible in the fiction section?
I would never read an innocuous meme comment condemning slavery and think “ah yes, time to make a point about religion being fake and bad”.