Blocking a receiver Question

[Juxone]

"It is never a penalty if the offensive player is acting like a blocker. Then the defender can hit them if they are an eligible receiver, unless of course the ball is in the air and in the direction of that receiver. "

I am actually talking about an offensive player who is or appears to be running a route and does NOT attempt to make contact with B-- Offensive player runs 10 yards and makes a post and is contacted by B before the pass .. ??