Once you get to a certain amount of Known on the internet or a subsection of it, or even in a subsection of a RL group of people, there are going to be people who will make up a version of you which exists only in their heads and which has absolutely nothing to do with who you are. It might better resemble who you were twenty years ago or it might never have had anything to do at all with who you were then or are now.
You cannot stop this. You cannot prevent this. Once you get a certain number of followers or a certain amount of attention, that's going to happen: people will make up stories about you which either look through a fun-house mirror at some small aspect of who you are and twist it and blow it up until it doesn't resemble you at all, or which just have absolutely no basis in fact whatsoever.
This is just another kind of parasocial relationship; it's the kind which really sucks to deal with, because it's so negative and so pervasive. It's very real, and the frustration you feel about it is very real. Nobody wants to be known incorrectly.
But. You can't control this. It's gonna happen. No matter what you say, no matter how precisely you say it, the people who want to misinterpret you will find a way to do so. This doesn't mean 'don't pay attention to what you say,' or 'don't be purposeful and precise with your language,' but it does mean 'don't obsess over the people who are determined to get you wrong.'
You can be the most anodyne, run-of-the-mill, unremarkable human being, and the people who are determined to hate you will find something that they can point to and say 'ha ha! I told you that Spider danced with the devil at midnight! I witnessed it myself!' (It will not help the situation if you are, say, self-admittedly stubborn as fuck, long-winded, and sometimes kinda fucking obnoxious, but please realize that in the end, it doesn't really matter. This is gonna happen no matter what.)
The people who matter will look at what's being said, wrinkle up their foreheads, and say, 'uh, man, it looks like Spider was actually playing with his dog at 9 am?'
That said, if you don't have elephant-thick skin from being a marginalized-gender human being who's been on the internet since before the web had pictures, there are some things you can do to make it easier when people making things up about you starts to get on your nerves:
Establish protocols for when it becomes too much: have someone read your messages, turn off your notifications, have time where you purposefully disengage.
Establish protocols for how you interact, period: "I will block people without guilt if they engage positively with the people who spread untruths about me." "I will answer everything in public so people can't lie about what I said, because it's right there in public." "I will not answer work-related stuff in DMs, that has to go to the work email." Whatever it is, create some boundaries for yourself. Stick to them. The people who push you to bend them aren't doing that for your benefit but theirs.
If you get someone who really hits your Weirdo Alarm, trust it. Yeah, block and report, but also, take screenshots and store them somewhere that isn't easily erased. I have an 'Internet Weirdos' folder, which makes it a little easier to deal with when people start doing things like 'making threats of physical harm to me and my family.' Don't fuss, just take a screenshot and chuck it in the folder. Having that record makes it easier to just forget that it ever happened, because you have a paper trail if anybody starts doing something Real Weird.
Spend time offline, with people who do actually know you.
Don't get lost in the version of you that someone else makes up in order to make up for the shit that's missing in their own life. You aren't required to play the part that someone else is trying to script for you. It is never to your benefit, only to theirs; you gain nothing by standing in that role for them, and you lose precious seconds of your one irreplaceable life.
You could be using those seconds to look at this video of how to pick up a duck, which I think we can all agree is a better investment of your time.
