Sue them for what, his own decision?
from the news story
" At the airport, staff offered to push him through the terminal on a high-backed wheelchair - an option he rejected as degrading." and "He asked if he could instead be transported in a motorised buggy. However, Luton does not have one."
Instead he decided to make his own way in what, by any standard, was a degrading manner and then have the termacity to complain.
Battle bowler on, awaiting incoming......................