You do realize that Meta will likely implement incentives to stay on their platform, and weed out other federations over time, right?
They're absolutely planning to grab Fediverse members, and will make efforts to prevent the other way around. Your friends will stay with the meta product because it's more convenient for them to do so.
You honestly seem to be more rooting for meta than the fediverse, since you seem certain that "anyone who disagrees could never be convinced otherwise"...but you seem to have only taken into account fediverse users doing this, not meta users. Like you're arguing very one-sidedly.
If you can't convince them to jump ship now, I just don't see what changes when Meta provides them (as meta users) more options, not less.