The problem with simple philosophies is they inevitably collapse in on themselves, as yours has in just two sentences. We can infer from the second sentence (and a later quote from the same post "I'm against moral laws... laws whose sole purpose is to tell adults how to live their lives when they're not hurting anyone but themselves.") that you'd be fine with the "hardcore drugs" if there deleterious effects were localised to the user. For whatever reason a company offering for sale a highly addictive product that makes you claw at your skin, grind your teeth to dust, and develop lifelong psychological issues doesn't count as "direct and proven negative impact on their neighbor". I guess because they should have just said no to that first hit! Have some self control people!
Never mind the huge information asymmetry between a massive company creating and advertising designer drugs and your average pleb on the street. Yeah everyone knows meth isn't the best for you, what about that new product Examite released last week? It's probably fine. I mean it hasn't been proven to have a negative effect on third parties yet right?
Of course, gambling actually is proven to have a direct negative impact. A flutter here or there won't do much (except to your bank balance), but develop a compulsion,
which is exactly what these games are designed to do, and your
brain actively rewires itself to make you retarded, permanently. If intentionally inflicting that on someone to make a buck isn't harm to your neighbour I'd like to know what is.