Nobody is immune to judgment - I can’t tell people not to judge based on appearance since I do it too. You can absolutely make educated guesses about someone’s mindset from the way they dress, but it’s a huge leap to then conclude that they’re a potential school shooter and treat them that way. Making fun of them online on the other hand is just mean.

If someone wears a swastika armband, they’re not leaving much to guess - they’re openly broadcasting their beliefs. That’s not the same as someone in tactical or military-style gear. This example hits close to home for me because I also like military apparel. I wouldn’t wear it to the grocery store, but I’d be pretty offended if people mocked me on a hiking trail for looking more of like a soldier than an outdoorsman and especially if they went as far as to call me a school shooter or a nazi because of it.