Read that again.
Why would a player do that?
You see, Thomas was holding out for a better contract prior to the start of the season and didn't get it. Therefore, when his season was cut short due to this injury, he no longer had any leverage in trying to earn additional money. Further, who knows if his career has taken a hit based on the nature of the injury? Some teams may not want to shell out money for his contract knowing he suffered such an injury.
The "hold out" for better contracts in the NFL is an interesting topic because it doesn't happen in certain other sports for a variety of reasons. In fact, it doesn't happen much else in life. If you sign a contract, you are obligated to fulfill your responsibilities assigned with that contract unless the other party or parties breach or violate the contract. Just ask any judge.
But in the NFL, there are some factors that make you begin to understand why players might hold out.
First, take a look at the career length of football players. It's very short. The physical nature of the sport does not bode well for people to wish to last long in the league. You're more likely to end your career due to an injury than to choose when it's time to retire.
Now, here's the big one. Unlike other sports, the money owed to NFL players is not guaranteed unless it specifically says so in the contract. So if you are cut from a team, the money stops. That's not how it works in a sport such as Major League Baseball: if a team releases you, they are obligated to pay you the remainder of the contract (with the possibility of a slight reduction in cost if another team signs you).
Therefore, NFL players hold out for better contracts in order to help guarantee that they will be financially secure if something happens to them physically and cannot work. Think of it as a form of insurance.
None of this excuses Thomas. His gesture, although understood, was probably not the best idea. And perhaps he should have taken the smart route and continued to hold out. But it focuses a light on something else: the system that governs the payroll structure of football players contains a flaw based on the ability to hold out, and it has consequences on multiple sides.
Imagine if your NFL team went from being a playoff contender to a hopeless pretender because your best player decides he wants more money. Would you immediately blame him?
The point here is that there is no clear cut answer. There are no heroes. This is more about debunking certain myths and asking people to take a step back and consider the bigger picture, which is one of the staples at understanding sportsmanship.