It is always beneficial because by doing so those observers who may be getting pulled into the fascist sphere see people that they normally get told demonize them trying to be reasonable and engaging in good faith were the side trying to "show them the light" is not. Sometimes thats all it takes to get people to reevaluate what they are engaging with and break the echochamber walls a bit. Remember you arent just discussing in isolation there are also the observers who you can aid as well. If those getting sucked into those spheres constantly get told people silence these ideas because progressives cant argue against them what do you think you do to the observers who see those posts getting removed without dialog? They start getting confirmation bias and pulled into those spheres even faster. Its the same reason certain religions send people door to door to spread the word of God, the point is to have those doing the outreach feel ostracized by the world so they become more ingrained into this group that "actually loves" them and is trying to act in "good faith" but is constantly shuned by the outside world. By just not engaging/answering questions or removing those posts you are doing exactly what they want you to do as it gives them ammo to feed their narrative of being persecuted.

I would say if you think you can tell someone is acting in bad faith. Call them out on that and explain clearly why it's bad faith. You can just ignore any response after that but I think it's extremely helpful to future readers if you can make them more aware of the tactics people making bad faith arguments use.

As op said. If you don't have the energy or desire to make a response it's more than ok to not engage of course. I would not want to wish arguing with people online against your will on my worst enemy.