Is it rude to use two train seats alone after booking both?

It is a matter of individual perspective.
Looking at the comments on the video above,
some say it is rude for standing passengers to try to sit in empty seats,
vs. those who say it's not that they wanted to stand, but that they were pushed out
because someone booked two seats.
What is the problem with using two seats alone that I paid for?
vs. even if you paid, it is rude to restrict the mobility of others in public transportation.
From this, derivative questions arise:
If this isn't a problem, is it okay for a chaebol to book an entire train car
to use with family or friends?
Is it also rude for one person to book multiple seats
for popular movies or professional baseball games?
Since those aren't public services like trains, there is no issue
vs. is it okay as long as you pay the money?
For these types of issues, social consensus is important,
but as the value of money continues to rise, it seems there will be more opinions
stating that it is not considered rude.