It did ( and has) affected my kid so I'm not sure what you mean by that. And I'm always appreciative of people that volunteer their time for my kid. I'm not trying to make it difficult for anyone but golly, my kid can't be in 4-h because I'm not on Facebook? Now that seems absurd. I'm trying to do my part and meet her halfway.
Unfortunately unless you’re the one controlling the group schedule it’s her prerogative. You may need to join back up or buddy up with another parent to keep you in the loop. The group leader responded fine and it really shouldn’t have provoked your ire. And I say this as someone who hates facebook and went without an account for years. This is the natural consequence of that.