I don't understand the racism here. Millions of white kids, consisting of every position in football, would kill to get a chance to play professionally. You're acting like only black kids are allowed to be linemen.
The racism isn't in the sport per se, it's in the society that makes the (dangerous) sport one of only a handful of options for some groups.
It's tough, because there's no clear, single "bad guy" to hate, but that doesn't make it any less shitty for the people living through it.
You'll typically see black players mostly represented in the 'skill' positions (receiver, running back, linebacker, defensive back -- basically any position that relies of speed and quickness). This comes from generations of racist attitudes pushing black players to the 'athletic' positions while keeping white players for the positions that require 'intelligence', 'grit', and 'leadership'.
Also, it's not just the line that suffers brain injury.