Why does there need to be a special day for the ATSAs you work with ?
At Scottish we treat them the same every day, that is as colleagues, part of the team, and above all as friends. No one makes each other cups of tea, and nor would we expect the ATSAs to. They are professionals with a job to do, the same as the ATCOs. They help make it work.
Maybe other units have a 'them and us' tribalism, but that's more to do with the people involved and their prejudices, than the job grades I would say.
At many units, having a good ATSA is the difference between sinking and swimming. So if an ATCO treats you badly, then don't go the extra mile and let him/her claw his/her way out of the mire without your extra help. Just do what you are paid to. Then the attitude may change