Unless I am sitting in J, nobody can recline in front of me. It's not that I'm a tool about it, it's just not physically possible given that when sitting in a normal QF/VA/JQ Y seat, my knees are squarely lodged against the seat in front of me. The person in front usually tries, then gives up.
On the few occasions they persist, I politely say "Excuse me, unfortunately I've got long legs and my knees are right up against the back of the seat. Please stop trying to crush my legs," and that usually sorts them out.
Only one time have the other pax gotten obstreperous and then I simply ignored them, pinged the CA and said "The gentleman in front insists on continually trying to recline his seat, which won't work because of the length of my legs. Can you either move them or move me? Or tell them to stop trying to crush my legs," and the CA told the person to stop being disruptive and pointed out that the flight was only BNE-SYD and surely they could remain upright for 45 minutes in the air.