The damage reduction from blast protection has no effect on direct hits from wind charges.

To reproduce:

1. Enchant a mob head with blast protection IV in creative mode.
2. Set up a dispenser with a lever next to it.
3. Fill the dispenser with wind charges.
4. Go into survival and activate the dispenser in front of you to hit yourself with wind charges.
5. Wear the mob head and get hit with wind charges again, noticing that there is no difference in damage.