Let's says I'm blocking with a Hitchclaw Recluse (a green spider with reach that is a 1/4) and I have cast the instant Woodcutter's Grit which targets the Hitchclaw recluse giving it +3/+3 + hexproof. So now it's a 4/7 hexproof reach spider blocking a Coast Watcher, a bird soldier with flying and protection from green and my opponent had cast Inspired Charge in retaliation.
Hitchclaw Recluse can't block Coast Watcher, even though it has reach.
One of the qualities offered by protection from green is that the creature can't be blocked by green creatures. Hexproof doesn't matter; the spider isn't being targeted by Coast Watcher. So the other instants cast don't matter.