This idea that poor Joe Johnson doesn't ever get a call was already tiresome before it made its way from the TV broadcasts to print. Joe Johnson doesn't shoot a huge number of free throws because he shoots a lot of jump shots and he doesn't have or doesn't use any explosive off-the-dribble moves to get to the basket.
Not all good players are good in the same way. I'm pretty sure that if Dwyane Wade could make 38% of his three-point attempts, he would not make such an effort to get to the free throw line. But he can't so he does. He also gets hurt a lot more often than does Joe Johnson. I think it's clearly in the Hawks' best interest that Joe Johnson play 82 games rather than shoot an extra free throw or two a game.
Or, if the latter is so important, let Johnson shoot the technical free throws rather than Marvin Williams.