Can someone be on a IP blacklist?

Today I got in a argument with a communist guy on Reddit who thinks I'm a Fascist just because I posted something about WWII and he said he was going to find out my IP and put me on some kind of blacklist that would prevent me from using my favorite military forums. It now turns out , that today I tried logging into the WWII military forum website I always go to it didn't let me log in and said I was spam.
What the hell !
I then tried signing up to another military forum website and it said the same thing !.
That I was spam.
What's going on here , did I really get hacked?.

Just change your ip or use vps. Then you are fine. If he owns the forums, yes he can blacklist your ip's, which will not let you log in. But just restart your router, change mac address. if you are having dynamic ips, after you restart router, you will get different ip. So you can login after that.

Its possible to get your IP blocked if you don't use VPN.

From what I can tell they probably (or at least is claiming to have) submitted your IP to a database or a secondary service that these forums use to automatically block spammed IPs. Think of it as a telephone book for spammed numbers. Maybe they just made an entry. Contact your forum admin and ask them if your IP’s been manually blocked for some other reason. If you’re not, ask to be unblocked.

Oh, this is incase you don’t have a dynamic IP or if they’ve blocked an entire range of IPs.

There's some websites that allow you to lookup your ip and matches it to blacklist db's, just give it a quick google and see if youre listed anywhere.

Yeah it happened to me

Use VPS or VPN mate you’ll be fine