It was bad defense and credit to Thomas for making an open shot, but when a guy spots up for 3 and makes a wide open shot, that means he abused him? JB over helped (something I've seen Mike and every other basketball player do 1000 times) and it was a mental mistake. It doesn't prove he sucks at defense.
He's not quick enough to defend quick and athletic PG's which we know by now and he's not big or strong enough to defend a larger 2 or 3. That can be a problem some games, some games it won't matter. He's not a good defender, he tries hard but he just is too limited physically. I'm getting tired of talking about it but it is what it is when people are comparing him to Mike when Mike was a very good defender