Bittrex recently delisted GLC and now users are contacting us unable to withdraw their coins unless they pay a .25 BTC coin recovery fee.

I guess since their volume has fallen to nearly zero, they have to find some way to pay the bills.
Actually, it was on their Recovery Policy (updated since 2017), not new :
https://bittrex.zendesk.com/hc/en-us/articles/115000961172Aside from Bittrex's notification about the token being delisted, have you informed people via your newsletter or social media accounts about it? If yes, then you and Bittrex did your part. Also, if the users put their coin/token on exchange, they should know the risks.