That's what the recline button is there for. No one has the right to deny someone else from reclining just so they can have more space for themselves.
It’s not about “more space” for me - it’s about my right to sit in a seat without having someone in front of me crash their seat back into my knees. What part of that do you not understand? I’m not suggesting that one should be able to say “I just don’t want you to recline.” This is an argument about the physical requirement of sitting in seats that have been shrunken down to the point where I literally have to wedge my knees in against the seat back in front of me at times. I try my best to get exit rows or economy comfort, but that’s not always possible because nearly every flight I take is 100% full. So, what am I to do? Just smile and say “awww, thank you for the pain?”