It's clear exactly what it means. Football is entertainment. It's why we spend the money. It's why they get paid. They're freaking up their bodies and minds for our entertainment. They get paid to do it, but it doesn't change what it is.
You're right. They have the choice to quit, just like you had the choice to quit. For Donald, there's a certain amount of money where it's worth him continuing to play. I would expect people to understand and respect that decision rather than siding with the billionaires who sit on their asses and collect profits.
If one of the people you worked with had demanded more money for the dangerous work you did rather than quitting, would you have said, "To hell with you man, you should appreciate the money they're paying you" and have supported the company you worked for?
Do you think you would have been within your rights to ask for more money to continue being a hazmat tech to make it worth the risk to your life? Would you think it nuts for people to be angry with you for doing that and support the owner of the business?