-They played good cop, bad cop with you (supervisor and manager). Don't fall for it. They rehearsed what they were going to say ahead of time. They are trying to manipulate you..." my manager is a great guy getting the supervisor off my back, I will work hard for him."
Notice that they steered the narrative that you are the problem and need to work faster.
Realize that the supervisor is just playing the role. He is a jerk for agreeing to harrass you, but make no mistake they train him how to do it.
How to deal with it?
Never let the harrassment affect how you work. They can tell you how to be more productive, and you should take that to heart, but not the harrassment. Just do your job. Keep your cool. File on all harrassment. If they say to work faster tell them "I will do my best". Don't let their mind games get to you.
Sometimes they harrass just to get your adrenaline up (get mad) ...and go faster.
Management are just temporary employees. I personally don't care AT ALL what they think about me. They have the right to tell me how to be more productive and safe, but nothing more.
Stare at them blankly, say you will do your best, file, and don't let them get to you.