I believe the trend is to stretch wire across the trails, or leave planks with nails in on them!
Joking really…
Sad thing is, there’s people out there who do that, and they aren’t joking.
When you’ve got people on mountain bikes being dickheads, people will think that mountain bikers are dickheads.
Only takes one of them to be not too bright and in possession of fishing line and someone gets hurt.
Whether it’s trashing the land, or riding inconsiderately or whatever, it reflects badly on anyone who rides on knobbly tyres. Whether that leads to access problems, vigilante idiots or just bad vibes, it’s right that it’s challenged by those that have the gumption, and good on you, OP, for not standing by or just being blindly tribal because they’re “mountain bikers”.