The slide is there for people to use. End of story.
I would have apologized at first, and suggested he move. On telling me he is not going to move, I would make some comment to indicate to him I’m still going to use the slide, such as maybe “ok, suit yourself” or whatever - the kind of comment he would dismiss.
No doubt he would bitch again next time you went down, at which point I would explain to him that there is a scenario where both of us can get what we want. He would understand.
I think your crazy dude. I work in a gym/pool area (no slides unfortunately) but i would have used it over and over again and taken great pleasure in soaking that jackass.
I mean, if the gym here is very busy and some tit is doing curls in the power rack while another member is waiting to squat, ill ask them to move elsewhere (in a polite manner of course but in such a way that its not up for discussion).
I seriously doubt using the slide on your off time and wetting some numb nut because he wouldn’t move his fat ass out of the way would compromise your job.
Your diplomacy is admirable but completely unnecessary.
Next time go nuts!!!
I would have soaked them first time down and had a good laugh while saying I’m sorry, also saying I didn’t realize they were so close. You know, play stupid like them.