That’s so sad, I’m sorry to hear that your last conversation was such an upsetting one. I’m sure they are right that he was not himself and it was the drugs talking, but that is still a horrible memory for you to have to carry with you.
A lot of people find that they struggle with bad memories of their loved ones last days. However, usually, in time, they find that can spend less time thinking about these, and more time thinking about the good memories. I expect that you said you loved each other many times over the years - that last difficult conversation can’t change how important that is.