I don't think it's fair to say it's a stupid rule. Every business has the right to set up their own rules around their employees taking drugs. Especially notable when the health of the players is a huge financial investment by the company. Or even companies where their employees use heavy machinery, etc...
People forget that the players didn't have to take the job. And if they can't give up pot for 5-10 years of their lives then they have bigger problems than being employed at that time.
I definitely see your point. The company I work for is very anti-pot and we are drug tested randomly. I spent last year fighting cancer and was not able to take THC pills because of my company rule. Well, it's a bit shady, but the rule was I could take the pills, but if I was drug tested, I would be fired. When you are taking 25 pills per day due to Chemo & Radiation, it's hard to keep them all down. Throwing them up doesn't do you any good. THC coats your stomach and allows you to keep them down.
Before I had cancer, I was very much against the players smoking pot. After a year in and out of the hospital and being told by actual doctors what marijuana can do for you in terms of helping with stomach issues, pain, depression, sleep etc. etc., I am not against it anymore and think the rule by the NFL is dumb. Only because of the pain these guys suffer from during & after their career. The NFL is all for giving them as many pain killers as they want, and not giving a crap if they get addicted (listen to Brett Favre's story). The NFL may have rules, just like any employer, but there are major differences. In ANY job, if you suffer from enough concussions, you can collect Work Comp. It's the law (and the field I work in). You CANNOT do this in the NFL. After enough concussions, you are simply out of a job, but you CANNOT collect Work Comp from it. There is no safety net for the player. This should be illegal. This is also the reason they continue to play through concussions. Someday, the NFL will be just like the Coal Industry in this country. They will be sued to the point they are not able to sustain it. It took 40 years for Black Lung to ruin the coal industry (in terms of profitability). CTE will do the same thing to the NFL at some point because just like Black Lung, those in control try to sweep it under the rug. Watch and see.