You are correct, a debate can be had.
I just don’t think we should have that kind of debate in the Great Debates forum. I think any resulting debate would be incredibly shallow. I think it discourages participation from other-minded posters and makes them feel (slightly) unwelcome.
If a person says, “I think all people who believe X have an ulterior motive”, and you believe X, it follows that the person thinks you have an ulterior motive. People ascribing bad faith to you at the outset of a debate is a good enough reason not to participate in that debate. Or that debate club, who thinks it is appropriate to offer up your good faith the subject of debate.
Moving past that, “I’m a person who takes position X, and I’m being honest” is the most intuitive counterargument for people who fit the bill, but also a trap that might indicate trolling: you can’t accuse another poster of being dishonest. So, why risk being branded as a troll - by moderators or by other posters? It’s easier not to participate at all.
You have said one can turn the debate into one over the honesty of some third party, paragons of position X who you think are being honest. This alternative was offered to me in private shortly after creating this topic. There is a point, I could argue that John McCain was a patriot who honestly opposed torture, or that Barry Goldwater really believed in state’s rights.
But that doesn’t seem appealing to me. I’m put on the defensive when implicated in a topic like the ones I have described. And the problem is that I’m implicated at all. That doesn’t change. Furthermore, I’m an expert on me, not Barry Goldwater. Defending him doesn’t necessarily mean defending me, and then I feel unfulfilled. Finally, chances are, any supposed champion of the cause did something which I disagree with, and white knighting might give off the wrong impression.
I mean, imagine trying to hold a debate but not being allowed to present your own arguments. Instead you can only pick somebody else and adopt all of their arguments. Your opponent can admit errors and adapt their position. You can only switch out your representative from a list of true Scotsmen that fit your opponent’s requirements. It’s a recipe for frustration.