I am not quite sure why you think those behind the people on the curb have more of a right to a good view than the ones that came early to get a prime spot. If you want to stand, stand. If you choose to sit, sit. It is hardly rude to stand up to take a few photos. When I use a tripod, anyone behind me can clearly see there will be an obstructed view, I can't really take photos when I am sitting below my camera.
IMHO I find it quite different than putting a child on my shoulders, or my husbands (which we have never done by the way). I am 5'4" and a size 4, most anyone can see over me or around me when I am standing.
You just set up your camera on a tripod and leave it there while you sit down? how have you not lost/broken your camera or tripped someone?
There are plenty of adults shorter then you and kids too...would you stand up in the middle of a concert, movie, or show to take pictures?
My Husband is a volunteer photographer for various nature and animal organizations, and also is an avid vacation photographer. If he was sitting down and stood up to take pictures during a parade or fireworks I'd tug him to SIT BACK DOWN...and give him my best 'annoyed wifey' stare.

(He has a giant camera with lenses and one lens is so big it has a HANDLE!)
Even as an amateur, my Hubby would never use a tripod in a crowded park, he uses a stick collapsible thing that has one leg.. MONOpod! yes! (thank you hubby.) IF he is standing, he usually stands next to a pole and stands the monopod so it is resting on the pole. it's eye level to him, in front of him, and not blocking anyone. We usually stand off to the side when watching fireworks and he stands in an area where he can get great photos and no one is behind him or near him (in WDW he usually stands behind bushes by the Crystal Palace...people are sitting on the porch with is elevated behind him...and he keeps asking me if he is blocking anyone...he's very considerate...!)
No one can trip over his monopod cause it's between his feet. When we go to public places, we ask customer service and guards if tripods are okay and because they say no so many times, he got this cool monopod stick, and that seems to be okay when he asks. This is not a selfie stick. This is a monopod. (My word for the day!)
If you are standing behind the people sitting, and no one is shorter then you when you are standing, and you are just standing, not moving all about... then you are fine, but you get up and block someone's view who is shorter then you...it's not viewed as positive by me.. I'm 5'1." I do not want to see the back of your hairdo or your really amazing camera...LOL!
I'm very sensitive about this whole tall people blocking me thing. (Yes, you are tall you got 3 inches on me!) I've never known what it is like to have a great view without effort, planning and usually spending money on a reserved area. (I had tears in my eyes when I finally got to see the electrical parade from the reserved FP+ section in WDW....I have only heard the music and seen the top of the floats...since I was 6 and was able to see under adult's legs...I'm 40 now...it's been a long time coming!)
I am sensitive to the fact that there are others around me and should get the same opportunity as I to see something wonderful and fun.

As a photographer, I'm surprised you have not come across this type of reaction in the past.