I think that might have been true a couple of decades ago, but I'm not sure if it's the case today.
A good recent example is ketamine. The drug, or, rather, the mechanism behind it, has gotten a large push research wise of late, since it was discovered that ketamine relieved depression using a mechanism that current anti-depressants do not utilize. Until further drugs are developed, "ketamine clinics" for off-label treatment-resistant depression also exist. And there really doesn't seem to be a huge issue made about them.
I would hazard a guess (unfortunately) that one of the barriers here regarding fundraising among more commercial interests is the lack of the ability to patent, which means that the rewards for making MDMA as a treatment are not as great, as far as commercial backers would be concerned. In the case of ketamine, drug companies are trying to develop chemicals that use the same mechanism, but do not have the hallucinogenic side effects (an example currently in Phase III would be Rapastinel). These efforts are able to get corporate funding. Also, MAPS is more "advocacy group" than "medical industry", not that there is a problem with that, but they might be outside the circle of what the typical drug trial fundraising process goes through.
If MDMA even remotely has a chance (the fact that it passed Phase II trials suggests this is the case), I definitely think it would be worth exploring, as current medication options for PTSD seem to largely be limited to anti-depressants (SSRI etc.). Ala ketamine, this would be a new approach.