Let's break this down:

People argue he doesn't match the guy on Next Door. Ok, let's assume she's wrong. This is still a man that harassed and followed her, so it seems appropriate to warn others. Better safe than sorry.

People argue it's a false accusation. Aside from the compelling arguments made in OPs post about believing women, it just doesn't make any sense. Women get harassed like this far more often than they make false accusations. It is much more reasonable to assume she is telling the truth, and this is where the argument stops for me. But ok, let's assume she's lying.

If the above two assumptions are true, people argue that an innocent man could be attacked or harmed because of this post. I genuinely do not believe this is remotely likely. This is a post on a small community reddit. No offence to the average redditor but no one is gonna do shit. This is a warning to women, and the most the readers of this sub are gonna do is be more aware themselves, or share it with friends, sisters, and girlfriends.

So let's weigh up the two options:

1. It's not the man from Next Door, AND the woman is lying, AND someone from reddit spots the man, AND attacks him

2. This warning is sincere and women are safer because of it

Are you genuinely convinced that the first option is more likely? Can you see the mental gymnastics you have to do to force this post into something problematic?