You're right! He was murdered because of our attitudes, and he won't get caught because of our attitudes. There is concrete evidence just lying around, but the police won't find it because of our attitudes. The investigation is done, the proof is in the pudding, but the murderers, who are perfectly known as the culprits beyond any doubt, will get away with it because of our attitudes.
Behind every perfectly reasonable explanation of someone's death is a conspiracy theory just waiting for the right nutjob to discover it.
What do you expec tthe police to do? They are holding an investigation into this death just as any other. In fact, they are giving it more scrutiny than usual - the forensics team wouldn't be called if it was just some joe schmoe off the street with a needle in his arm.
If they find something that points towards homocide, they'll investigate further.
But it doesn't matter.
It's because of attitudes like yours that this death will live on in infamy as a conspiracy hushed up by either the government, or the rich and powerful, or both.