I think any driver defending in a manner that puts the other driver at risk should be penalized. That’s not a controversial opinion, we literally have rules against such behavior when it’s very obvious (break checking and weaving). In this case he slowed down into a turn where he was guaranteed to get in Russell’s way. Even if Russell had reacted in time he still would’ve been forced to slow down because it would’ve been next to impossible for him to pass Alonso in that turn. And we know what happened when Russell didn’t react in time. It’s erratic driving by Alonso and that deserves a penalty.