Some people are insulting me

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Hi! im new here :) I am 20 years old boy.I have been fighting with axiety with many years now.Still recovering slowly.Big thing that helps me is that i quited porn and masturbating(no shit). But still i have some anxiety. I work with many different nationatilies students at warehouse. I cannot understand why people sometimes instult me. Yeah i dont talk that much but i am friendly and talk to them all. Today one guy just told me:" you should see a doctor,you are crazy man. Sometimes i get paranoid thoughts when i see you. You could just come one day with a gun and shoot us all". I have never told him anything bad but wtf.It could be ok if he made it as a joke but no,talking loudly in canteen.Nobody cared that i was hardly insulted.I am not used to this and dont know what to do about it.Most likely i m going to say something about him tomorrow but why he sayd that in the first place.Maybe i look different because i havent recovered from anxiety completly but still.
Maybe someone could tell me some ideas.I will be working there for long time and i dont want to go to work thinking about these stupid people.