I think declining is inconsiderate with how small seats are today especially when the people behind you can't recline themselves. Looking at the clip, it looks like the guy is in the back row and iirc most back rows can't recline, if that is the case then he can't make extra space himself. She would be literally taking space away from him. Regardless his behavior is bad and in no way justified, if he has a problem with her reclining he should try talking to her and if she refuses talk to the crew and see if they can mediate.
For me personally, I am a big guy, so much so I need to get an extra seat so I'm not encroaching on the person next to me. This means the small forward space is even less for me. When people recline in front of me, it means the seat back can be touching me, now imagine having an 11 hour flight with the person in front of you reclined sleeping and you have less than an inch of space. Now did I hit or do anything to the seat or person in front of me? No I just endured it because it isn't the guys fault that I am overweight but I won't recline because I understand all to well how uncomfortable it can make the person behind me.
Ultimately I think they should remove the recline functionality because it is dumb that someone else can encroach on your space and you have no way to move or compensate for that lost space. Oh and the argument that you paid for the right to recline, no you paid for the right to sit in a seat and that is it. If crew asked you not to recline for whatever reason you'd have to do it. Hell they can force you off the plane even if you paid for the ticket.