When you have a mental illness, it's like you have an amorphous monster that follows you everywhere. If it's depression, it can sit on you like a lead onesie a lot of the time and make it damn hard to move, and it can cover your head and make everything dark and drab. If it's anxiety, it can whisper nasty things to you and sometimes shout them so loud you can't pay attention to anything else. If you have trauma flashbacks it can cover your whole body and force you to watch videos and listen to sound of awful things, and even if you can see through it, you can't stop it and you can't escape it. If you have a different illness I'm sure it does other things, but I can only speak about the ones I've experienced.
It can be awful to have this monster, especially when it contains multiple varieties of mental illness. But it can also be fucking awful to be around someone else who has a monster. It can be torture; at its worst it can be abuse. So people have a responsibility to manage their monster as best as they can to keep it from attacking other people. Just like if you have a pet who will attack people -- it's not your fault if they attack someone, but you need to do your best to care for them, train them on how to interact, and keep them on a leash when they're out. And if you know what sets them off, you need to warn people so that they don't end up getting bitten when it could have been avoided.
I have known people who have the most massive, powerful monsters and yet they keep that thing on a leash and it almost never bites anyone. It will blob over them and scream at them from every direction, and they will quietly tug on the leash and pull it away from people so that no one is hurt. They know that it lies and so when it tells them "that person doesn't like you" they don't accept this and they ask the person. They know it predicts things that won't happen and so they refuse to believe it. When their monster is incontinent they take it outside, and if it makes a mess they clean it up. Their monsters are not dainty or polite, but the way those people handle them you might think they are. Some people I know have monsters three stories tall yet I've barely heard a peep out of them.
And then I've known people who don't bother leashing their monster at all. Who will sit and watch while their monster rips someone to shreds, and later say "it wasn't me" or worse yet, have no comment and try to pretend that it didn't happen. I've known people who let the monster shit anxiety all over people, instead of taking it outside to poop -- and then complain when the person takes time away to go shower! I've known people who refuse to feed their monster and let it climb all over other people desperately begging for food. I've known people who get angry when someone who has been feeding their monster stops, because now the monster is grumpy and loud again and is turning to them for food when they had gotten used to ignoring it. I have been most of these people, as well. Sometimes I slack off in training and my monster starts getting rude and gross again.
It's never your fault when you have a monster like this attached to you. But it is your responsibility and no one else's. It's your job to feed and tame your monster so that it is as respectful and kind as possible. It's your job to take it to excrete waste away from other people, or perhaps with the attention of a monster vet. It's your job to keep it from attacking people with words or deeds.
If you have someone who has offered to help you tame your monster, that's awesome! Just don't try to leave it with them. It's not 'help' if the other person is fighting your monster while you do nothing. Just like a rowdy pet, if you don't train it, it will get worse and worse no matter what people try to do from outside. You have to tell it no. Every single time. And when your monster damages other people? That's on you. You are the only one who is responsible for your monster. It's shitty because nobody signed up to be a monster-keeper, but it's yours now. And if someone who usually helps is not up for it, don't complain to them about it and don't make them feel bad. Your monster is NEVER someone else's responsibility.
You can have terrible monsters without those monsters constantly hurting others. Training monsters is a learning process and no one does it right all the time, but if you don't do your personal best to keep your monster from hurting others, then you are just as guilty when it does. I'm not suggesting that you avoid all people if you have an unmanageable monster. I'm suggesting you use every tool you have to tame it, and in the meantime you warn people about how the monster sometimes acts, and when the monster does make a mess or cause damage, you do the cleaning up. On what is possible for any given person or situation, I cannot guess and certainly cannot comment; only the monster-keeper knows if they are doing their best.
I don't think I'd feel fully at ease around someone who had no monster at all, simply because I think it would be hard for them to understand monster-keeping which is always a pretty big part of my life. But I also know that my monster is very suggestible and if I spend too much time with someone who has an out-of-control monster, mine will get increasingly difficult to handle. And despite not having physical form, these monsters can kill. So for me, it doesn't matter the size or type of monster; I feel safest with people who have a monster, but keep it in line most of the time.