On the subject of speaking several languages I have a friend who is able to speak Italian fluently as a second language and one day she and a friend were walking down Weybridge High Street in Surrey and commented in Italian that the lady walking ahead of them had a very big ar*e and those leggings didnt do her any favours at all.
To her horror the lady turned around and replied in perfect Italian that she'd heard everything my friend had said and furthermore my friend wasn't looking too good for her age and perhaps best not to assume that she would not be understood.
As for the two wrongly seated I am glad OP stood their ground. I hope that the man has sore knees after being so childish.