Their party was on May 6. I don’t know of any holiday on May 6 and certainly not one involving construction hats. The university is knee jerking bigly.
And it wasn’t the 8th of May, either.
The primary sin appears to be the construction attire which is “cultural appropriation” of clothing appropriate to construction workers. Look out for Cultural Appropriation. It is more insidious and more sweeping than anything PC that has come before. It will spread through the society and make everyone feel like he is “in costume” either appropriately or inappropriately and feel that everyone is looking at him and judging him by the role he assumes or expropriates by dressing (and/or speaking) the way he does. Ultimately we are to have n Agency that determine what we may wear and how and what we ma speak to keep us from “culturally appropriating” the ways of others that will all be rigidly defined in the Rules.