It is a verifiable fact that sharing needles can lead to HIV transmission.
People's opinions on the morality of illegal drug use are, or should be, irrelevant.

If someone makes the link between drug use and transmission, claiming they are opposed to illegal drug use does not change the verifiable fact that IDU facilitates transmission.

I was asked to set out my views on homosexuality.
I am open about those views and have expressed them before, but I was disappointed that it was felt relevant in what should have been a purely dispassionate, scientific/technical discussion.

Claiming someone is a "bigot" has been used as a reason to ignore a verifiable fact that that has been put up for consideration.