You can't do anything. Trust isn't moderated. The only way to get the trust feedback removed is if you talk to the user who gave it to you (The Pharmacist) and he agrees to remove it (I doubt he will).
And you don't need to have done any trade with the user. You are an one-liner shitposter and that's what the trust says. So it's probably valid.
Not everything needs a paragraph to explain. Especially when you are a newbie. Any advice given as a newbie is brushed away since you are infact a newbie and should still be learning the ropes. This is the newbie section after all. This should be a safe place to post quick comments and thoughts without fear of being belittled by people.