Seeing the reaction to the bridge, it seems that most Mastodon users don’t want AtProto to be compatible with ActivityPub.
If Bluesky was just another ActivityPub using site you could just defederate from it. This isn’t really possible when there are many bridges that relay messages.
But you also seem to have completely misunderstood what people objected to about the ATProto bridge. It wasn’t the optional possibility to reach people on Bluesky. It was the automatic opt-in that most people objected to.
By using the Fediverse, you implicitly opt in to having your content federated between different platforms. How is this any different?
Not between platforms but within the Fediverse. Bluesky is not part of the Fediverse.