Don’t listen to these idiots. Best case HR writes up a report and nothing else happens. Worst case you are out of work. Everything that happened till now can be explained away as innocuous.
Write down all the little instances and keep records. Also always record your calls. when you have something substantial maybe a chat or email then and then only forward everything to HR.
That’s if you actually want to raise a POSH. It looks like you don’t report to this guy. Practically it is better to ignore some comments and move on.