Like you’ll need to hide everything new you got into in fear he’ll yell at you or humiliate you for buying a new game or watching a new show, or even wearing a new shirt. Would you hide that you still celebrate Halloween, Christmas, birthdays, etc despite not being a little kid? Is it normal to go by keyspam usernames and be as anonymous as possible to avoid being found online by your friend as he’ll post private information or hate on all of your posts? While also seeming like the asshole because you’re being secretive for no reason?
Sounds like you need to distance yourself from this individual. They are not your friend.
A normal friendship does not leave you anxious or scared of their reactions no matter what you are up to, however private you want to be or how little time you spend with them. You don’t have to agree on everything or enjoy everything the same way. A friend is someone whos company you enjoy from time to time. But have no obligation to please or requirement to spend time with.
Posting private information about you on the internet sounds very bad. I’d ask them to refrain from that. Escalate that to relevant authoity if it doesn’t stop.