I'm going to not let a uniformed service member sit in my assigned seat on a plane
Why don't you want to let him take your seat?
He has no right to push me around just because he wore a uniform.
With air security the way it is nowadays, it's okay to want to sit in your assigned seat on a flight. But, you should still be accommodating and polite to others, military or not, if asked. Talk to the staff and see if a compromise can be reached.
Why do people keep telling me this. It's my right to sit in my designated seat.
Of course it's your seat and you're not obligated to give it others but it's not nice to be so stubborn about it. As I said talk to the staff and try to accommodate service member too, probably you'll get a better seat!