It may be helpful to make the distinction between practicing Buddhists (who undertake the precepts, meditate, and perform other practices advocated by the Buddha) and non-practicing Buddhists (who don't engage in Buddhist practice, but may subscribe to essential tenets of Buddhist philosophy, or are Buddhist by name alone). The former is a practitioner, and the latter more of an arm-chair philosopher who picks and chooses which parts of the Buddhist teachings they like, often to the neglect of the Buddhist path.
With that said, drug and alcohol use, in any quantity, are fundamentally incompatible with the Buddha's teachings, both practically and philosophically. The fifth of the five fundamental precepts observed (willingly) by devout practicing Buddhists (who take the teachings of the Buddha seriously) is to abstain from intoxicants altogether, not just from becoming intoxicated. In other words, a serious Buddhist practitioner abstains from drugs/alcohol and makes a sincere effort to avoid indulging in craving. A non-practicing Buddhist (if they are at all familiar with the Buddha's teachings) at least acknowledges that intoxicants are an impediment to clear seeing (according to the Buddha's teachings), regardless of whether they agree or disagree, or whether they are conscious of the effects or not.
However, I would not automatically associate drug/alcohol use with liberalism. That would be conflating liberalism with hedonism, an extremely common but blatantly inaccurate association that does not do justice to either.