Low level disruption is disruptive. The child doesn’t have to be doing anything super-naughty, it’s the persistent chatting, poking others, fidgeting, etc, that causes disruption. I often move children if they’re doing this. It’s not so much a punishment, it’s for their benefit and that of the whole class.
All children have two warnings, but sadly some just can’t stop themselves continuing. Then they get moved. Usually, they’ve got into a chatting/poking/messing around thing with their neighbour and, after an appropriate amount of warnings, the only way to stop this is to move one or both of them.
Your ‘kicking a paper towel while queuing for the bus’ is half the story. Ask yourself what the other half might be? Had the teacher spoken to your son before? Had she been waiting for the children to queue up sensibly for ages, given them all a final stern warning - and then suddenly your son kicks a paper towel. Of course, he’d be picked up on that.
I suggest you talk through with your son the occasions he’s been moved.what he’s been doing, if there had been any instructions or warnings, what the other children were doing, what it would be like to be trying to explain something or get ready for something and have random people chatting and giggling, distracting others, and not listening, etc etc. Explain it’s not personal. It’s his behaviour that’s been criticised not him as a person.
I’d also explain that there’s a lot to learn and get through in Year 2 so he’d do better to sit and concentrate and then he should find he’s moved less. You could even speak to the teacher about this so she can monitor him through the week and make encouraging comments if he’s sitting nicely/listening well/whatever.
Your son ignoring her when she spoke to him was rude. You’re doing him no favours by indulging behaviour like that. He’s probably feeding off your attitude and thinking he’s being ‘picked on’ when, in fact, the far more likely answer is that he’s messing around doing low level disruptive things and it’s that that’s getting him moved.