I really think that BB defense is overrated. What we need to do is play good poker all the time. Whether we defend or not depends on all the same criteria that we use for whether we call a raise or open the pot.
If we fold every time we are in the BB, our bb/100 would be -110bb/100 (-100 for the BB and -10 for the antes). The SB would be -60bb/100 and all the other seats would be -10bb/100. When we defend a hand by calling but then fold on the flop to pressure, then we will be -310bb/100's in the BB. The point is that defending the blind needs to be considered in the context of the strategy for the hand, not just calling the pre-flop bet. Defending costs more chips than folding and if we have a poor hand, let it go.
The BB is the worst seat in poker to start with. We have to invest without knowing our cards AND we will be OOP for the rest of the hand against 90% of the players. Calling a pre-flop bet with a worse hand than we would have called if we were in MP or the CO or something, has us playing poker at a disadvantage every time. Why would we do this? They will tell us that we have great pot
odds due to our calling discount. This is true, but the math doesn't really support playing terribly just because we have a discount.
I know some of this is contrary to what the poker community is trying to tell us. In 140,000 hands, my bb/100 form the BB is -20bb/100. This is better than any of the players I am playing against. It is very difficult to have a +bb/100 from this seat. We can lose 1bb when we fold or lose 3bb when we call and then fold (3x more). So minimizing our losses in this seat is the best we can do and part of this strategy is to not invest 3x more in our bad hands.
Play our solid ranges and play good poker. If the BTN or CO seem to be abusing us, then we can easily have a range advantage on our calls against them and we will do well. Just play good poker, always.
Good luck and God Bless.