I yearn to ask men who're practically sitting in the box splits on public transport if they've seen a doctor yet as something is obviously terribly wrong.
However, I did once tell someone he had to move his bags on a packed tube. He was taking up the seats on either side of him with his stuff & the tube was rammed. There were people standing all along the carriage so I actually had to peer round someone to tell him he needed to Move. His. Stuff. And. Let. People. Sit. Down.
I was once on a VERY busy train in SW London coming up to Waterloo. I was on crutches but no-one would let me sit down. I was held up by the sheer press of people. Before I passed out and/or threw up (and I would have been aiming to splatter as many people as possible, yes) two women from the group who'd been deliberately ignoring my request for a seat & my general presence alighted. I moved to sit down and had to ask one of them to move the tiny handbag she'd just put on the vacated seat. She then claimed that she'd not noticed me standing. Ahahahahahahaha.
On Saturday I asked an aisle!sitter (we were at the startpoint of the route, incidentally) to let me sit down. She glared at me as though I'd asked her to sign all her worldly goods over to be & then swivelled round in her seat. I was carrying a biggish rucksack & a large cloth bag of food shopping, clearly visible to her. I tried to squeeze past & rearrange my possessions without clobbering her only for her to leap up & stalk away. The couple sitting across from me had been watching all this & proffered the opinion she was clearly bonkers & I was better off without her sitting next to me. (They were right as my bag turned out to be able to have a seat of its own the whole journey despite my hoiking it onto my lap at each stop ready to let someone who wanted to sit down.)
I have to ask people to let me sit down - including giving up their seats - because my disability means I cannot stand up on public transport. It is incredibly painful & because I cannot compensate for the movement of the train I will inevitably fall & [partially] dislocate multiple joints & risk snapping a brittle bone or two. Most days you can't tell this just from looking at me, but I loathe the times I have to literally beg for a seat, offering to show my DP Freedom Pass/Railcard or my Blue Badge & explain what will happen if I don't get a seat. I get people simply gawp at me, I get people wait it out in the hopes of Someone Else Getting Up, I get tutted & harrumphed at, I get whispered about: it really is grim. I have reached the point where I routinely take out the wee folder I keep documents in & pretend to hunt for something so I can show the staring!people my Blue Badge. Last summer I had a bad fall on the tube after no-one would let me sit down & I tried to make it along to the next set of seats to ask there. The woman who'd looked up at me as I asked at given me a filthy look came charging down the carriage to "help", which meant ignoring everything I was saying, trying to haul me up (I'd only just put my sodding shoulder BACK) & in-between trying to insist she should pull the emergency alarm told me I should have ASKED for a seat if THIS was going to happen. Erm...
People are really quite horribly behaved on public transport. I wish I could magically distribute appropriate punishments/rewards...