What's your definition of 'salty'? I think you can definitely be politely salty, and dang's comments are all saying (at least) 'don't do that' which seems to fit.
My understanding of the word lines up pretty well with the Merriam-Webster definition (https://www.merriam-webster.com/dictionary/salty): feeling or showing resentment towards a person or situation; bitter.
By that standard, just telling someone not to do something wouldn't be salty. Salty is telling someone not to do something because only an idiot would do that.
By that standard, just telling someone not to do something wouldn't be salty. Salty is telling someone not to do something because only an idiot would do that.