It depends on the audience for those drugs and their relationship to the people making laws. Take, for example, crack versus cocaine. Crack and cocaine are nearly identical drugs. Crack has the same sentence for one gram as cocaine does for eighteen. (The disparity used to be five times greater before 2010.) But crack users are more likely to be black, low-income, and less educated. I can't imagine why they'd be a preferred target for "tough on crime" legislation. Aside from, y'know, systemic, institutionalized racism (and good old-fashioned poor-stomping, but it is well-known that the War on Drugs was intended to target black people).
Similarly, LSD was widely associated with undesirables in the sixties and seventies--counter-culture movements. Do you have a better way to provide yourself with cover for attacking them?
If you're surprised or skeptical of either claim, I recommend you read Dan Baum's recent report regarding his discussions with John Erlichman and H.R. Haldeman's diaries[1] (themselves available in the Nixon Presidential Library). Both men were deep in the Nixon White House during the formation of the War on Drugs; it's illuminating stuff.
[0] - http://harpers.org/archive/2016/04/legalize-it-all/?single=1
[1] - http://www.nytimes.com/1994/05/18/us/haldeman-diary-shows-ni...