The rational part is merely that it's an analogue that's more potent and longer lasting than ketamine, with evidence supporting the theory that health problems owe directly to the mass and frequency of ketamine consumed by abusers. Thus, it's rational to assume lower quantities of MXE will be consumed less frequently than the same users of ketamine. That's the extent of the harm reduction rationale of its design relative to ketamine on the assumption that it acts in similar ways in the body based on structure and subjective effect -- there's no claims of harmlessness or remotely similar. The ambiguity of that description is seized on by users and the blanks happily filled in by assumptions that it implies more than it does by those looking to justify what they know is overuse (not claiming that's you, just noting how rationalizations work). It's possible that MXE could be far more damaging than ketamine in other unknown respects, or even that it's more damaging to the bladder and kidneys than ketamine by some unknown mechanism that was never suspected. No drugs are rationally designed to be chronically abused to get high -- even Children's Tylenol causes kidney damage at high levels -- because abuse is completely irrational so far as medical function is concerned.
Quoted for some really good points. Who's to say whatever changes they made to mxe, did not increase the damage done relative to the increase in potency compared to ketamine? Mabey the damage is from whatever position they fiddled with to get MXE, and MXE is just a more potent (with different affects of course) ketamine roughly speaking. They could be right though, i just havent seen any compelling evidence MXE would be any safer than ketamine in terms of bladder/kidney damage, just because its more potent.