I'm sorry, but I will do this: I used to think like you're thinking. Pointing other people's logic fallacies, understanding sophism and the logical soundness of arguments.
Logic, for human debates, is very nice in theory. But there is a reason humans adopted shortcut thinking and don't use logic all the time. We are not robots. We don't have infinite processing capacity, and statistics and probability save A LOT of time. For example, doing strawmen fallacies is useful. It allows you to filter through a lot of crap before investing time in digesting whether what that person said makes sense or not. If you would go into any conversation with a blank state of "Let's analyse the logic here" Good luck with that.
So we adopt shortcuts. What shortcut is he doing? "I'm like you" is indeed establishing commonality. The person is saying "I get where you're coming from, i've been there, so I understand at least some reasons why you currently think that way." This is useful if the person is being honest because it let's you know that this person might be saying something more valid than if they had no idea where you're coming from. It means they were once in your position, and something made them switch. It's different than if they never had been in your position. They never had to think anything through. So knowing this is useful. This saves time. Is it fool-proof? Not really. People can lie, or might have not thought that much about it anyway, but like I said people are not robots, and we can't analyse each argument like if we were one.
So rather, let me also help make a shortcut and your argument more clear: Don't call out this behavior, which from an honest person is good, call out what you're actually thinking that he's doing - that he's trying to manipulate readers. Why you would think that, I don't know.