What constitutes a defenseless receiver? If his arms are extended exposing his ribs, should the safety, corner or LB have to wait for him to catch the ball and get his arms down before hitting him? Might as well play two handed touch in the secondary.
Why is a running back basically allowed to be tackled in any fashion (except horse collaring) and quarterbacks and WRs get protection.
Why are 300 pound linemen allowed to butt heads on basically every snap and that's okay?
Tackling has become almost impossible for the defense. A WR catches a crossing pattern sees the tackler at the last second and ducks his head creating a helmet to helmet, why is that the defenses fault?
The NFL has done a lot to try and limit the collisions, but to try and save these guys from themselves is impossible. Football is a high impact collision sport and every one of the players in the NFL knows the risks and has weighed those risks against working 9-5 like the rest of us and have chosen football. I don't want to see any player have issues after football, look what it did to Mike Webster, Steve Courson, Junior Seau, etc., it's tragic, but they all know the risks. Ryan Clark admitted yesterday or day before that he's has reconciled with himself that he will have health issues when he's still relatively young, but he continues to play.
The incongruities of who gets the protection and who doesn't is what doesn't sit well with a lot of people. There are very few rules protecting linemen, hell, they modified the chop block to be okay as long as the guy making the chop block isn't more than one player away from the person he is chopping. If it's dangerous to chop block, it's dangerous to chop block and should be eliminated from the game, but linemen aren't the marquee players, so they don't the same protection.