Got physically disciplined at Kroger

(Like it says in the title this was at Kroger (location: Kentucky) so this was already typed up for the Kroger sub so I apologize if some of the terminology is confusing) So this is a long story but I’m going to try and keep it as short as I can. So I’m filling in supervising cause our front end lead is on vacation. I don’t like doing it but I’ll help out if I can. So I clock in today and the other supervisor says we’re slammed and is just gonna use me to get breaks and lunches caught up easy enough. I start out on someone’s lunch on U-scan we’re about 20 minutes into my shift the other supervisor does an observation on me and says I passed I just need to be better on my greeting. Then our main boss stands behind me for like 30 minutes after this happens. Once he walks off she sends someone to take over for me I go to check in and see what they want me to do next. It’s the manager and the supervisor my supervisor says you’re gonna go outside and push carts again that’s fine it’s 95 degrees but I was fine with that cause again unjust helping out I’m not gonna complain about working. Then the manager says “do you know why you’re going outside” and responded with “I’m guessing it looks bad” and says “no it’s cause you weren’t doing your friendlys on uscan if you don’t take it serious your only gonna push carts and and bag form now on” so I start asking him what was I doing he said I wasn’t greeting and had my hands in my pocket first off my hands were not in my pockets (not sure what his obsession with this is btw) and I had been greeting people after the observation. So I told him that he just told me no you weren’t. Then I asked how was I standing and how should I properly stand he couldn’t show me exactly how my hands were in my pocket he tried showing is hands in his pants pockets so I responded with “that’s weird because I can use my pants pockets because my keys scratch me I always just use the vest pockets” he didn’t really have an argument back for that then I said I had been greeting people maybe not every single person but enough to not be getting talked to or punished for and I suggested we look at the security cameras to see everything I did wrong and he just mumbled “I saw it for 30 minutes then started walking off”. I ended up being out there for over 2 hours. My supervisor told me when she was getting ready to leave that she had no idea what he was doing and just did what he asked telling her to pull one of our two cart pushers in to bag then he told her to observe me. Essentially trying to find something for me so he could send me outside in 95 degree weather that felt like 108 with no help on a Sunday evening. He told me I was “being punished” and pretty much was an example Ive already went the union they’ve involved but I wanna do everything I can I want to make this huge and bad for him what else should I do? Is there any lawsuits that could maybe even be filed