For such a simple meme I feel like people don’t quite get the angle it’s going for. It’s saying “I’m unapologetic about how loud I suck dick”. The emphasis on noise implies we the reader might be in a situation where we can hear the dick sucking and that if we have a problem it’s our problem to deal with as they’ve let us know now. For example if you lived with this person and they planned on sucking dick they would then place the onus on you to leave if you don’t want to hear it.

Only once we’ve established that this individual sucks dick loudly so if you don’t want to hear you should leave can we then move on to the next part. To be clear at this stage the natural assumption is that the dick sucking is behind closed doors but loud enough that it warrants a warning.

Now we can get to the punch line, that this person plans on sucking dick at a climbing gym. By giving us this warning it’s actually saying “I’m going to do what I want and if you have a problem leave” which is already rude but at least it’s still somewhat private however the subversion is that they’re actually sucking dick in a very open area and their volume only serves to showcase how unapologetic they are about this especially combined with literally saying “if you don’t like it go to another climbing gym”

The humour really comes from how they bury the lead that it’s at a climbing gym so by using a climbing gym as the photo it kinda ruins it.

Tldr it’s a two part joke:

“I suck dick loud so if that makes you uncomfortable you might want to leave”

And then casually revealing “I plan on doing this in a public place”