[gknoy]

I think you mean https://en.wikipedia.org/wiki/Motte-and-bailey_fallacy :

    An arguer conflates two positions that share similarities, 
    one modest and easy to defend.. and one much more controversial....
    The arguer advances the controversial position, but when challenged, 
    they insist that they are only advancing the more modest position.

Thank you for pointing out this argument fallacy. I've certainly seen it and been unable to articulate what is going on and why it feels like an argument in bad faith, and now I have a name for it.