If I recall correctly, around 1850 or so the state said it was ok for you to end the life of your property if you wanted to. Would it be ok for you accept money to kill for them? Would it be ok for you to knowingly sell poison to someone who was going to kill one of their slaves? It was legal to do, so it was a “right”, correct?
If the pharmacist does not want to sell the legal drug, then they ought to work in a store that does not sell it. It’s like a clerk refusing to sell condoms because they are Catholic, or some one refusing to sell bullets because they could be used to kill someone, or a Muslim refusing to sell a customer alcohol, it's simply ridiculous.
I understand you oppose the drug, and thats fine. A solid argument can be made for banning the sale of this drug. But, until it is illegal, the public has a right to buy it at store that sells it. If you do not want to sell it, the work somewhere that does not stock the item.