The green means that it's technically inferior than WhatsApp, iMessage, Signal, etc. and/or you can end up with surprise international texting charges from your mobile network.

I don't have a problem with people discriminating against MMS, but everyone I know doesn't have a problem using any of the other decent alternatives that work on both Android and iOS.

Sounds like the green messages are doing people a favor by pointing out garbage people who discriminate against someone for not using iOS.

I'm just claiming that there is a valid use case for making it abundantly clear if a conversation is happening via MMS versus iMessage, so I didn't take it as a way for Apple to somehow "lock" people into iMessage...especially since plenty of other chat apps are a few taps away with no degradation in usability.