If I remember correctly (been a long time), I think SWG had drugs back in the day with some fairly severe consequences(could be remembering wrong though). Conversely, I don't like the way WoW does it where the blur is kind of annoying but kind of funny at the same time. The benefits are immediate, which is realistic, but then the consequences are very short and with no longer-term repercussions at all.
To address what you're saying directly, I don't think it would be very common for murder or suicide to be mistaken as recreational in real life. It does happen with murder I suppose but that involves some deeper psychological constructs that wouldn't be quite as common as the dissemination, availability, and exceedingly slippery slope drugs can be to the perfectly psychologically sound prior to exposure. Did some research on the effects of violent video games on children in the past and personally, I often found evidence of prior abnormal behavior not related to the game in question. Unlike with drugs, there's little question as to the permanent implications of murder and suicide even in children. They understand they won't respawn. Drugs can be a bit different though, in that the longer term repercussions are not obvious, they're somewhat hidden and easily disbelieved or ignored. The biochemistry feeds upon itself as opposed to the murderous, socio-pathological mind that is not a learned behavior.
Even in this game, just about everyone agrees with an alignment system that would impose repercussions on the decision to commit murder. Some (myself included) have suggested those repercussions to be substantial. That's not so much out of fear that it will somehow glorify, excuse, or promote murder in real life but rather to avoid excessive nuisance.
To me, and perhaps only to me who knows , drugs are inherently different. The implications are more difficult to drive home, and the biochemistry is completely under the hood and as such, completely elusive. The consequences are more difficult to teach as they are not as easily conceptualized.
In the long run, to have drugs in game, not complaining... it's a choice to be made, just requesting the implications be well thought out. I don't think that's unreasonable
To put it in terms you might find more agreeable, if you want the rewards of immediate gratification, there should be very substantial and tangible risk involved. There should be no question as to the risk, and the consequences of the decision you make.