It’s illegal at the Federal level, but we don’t take guns away from criminals unless they’ve been convicted. What’s being suggested here is that the mere fact you’ve been processed as a medical marijuana user is treated as a conviction for a marijuana crime. I don’t think that’s appropriate.
The 4473 form includes a question on drug use. There are legal ways to do firearm transfers without a 4473, but none through a FFL. Lying on the 4473 is the crime.
By the way, I agree that the setup is “inappropriate.” I think it’s beyond inappropriate. I certainly wouldn’t deny arms to white collar felons.