Judging from what I've read and my own experience MXE seems to magnify the ego in a much "cleaner" way than most other drugs. What I mean by "cleaner," in general terms, is: alcohol may magnify the ego, but it's clumsy; cocaine, meth, or similar stimulants may magnify the ego, but they ramp up people's baser bodily urges (sex/violence) to the point of volatility. MXE magnifies the ego, but it dissociates one from their body, too, and this may be what, for some people, allows it to be a more faithful but amplified representation of their sober ego relative to what other drugs offer.
If you become an intolerable ass on MXE alone, even more so than with other drugs, it's likely that it's because you are, in fact, an ass.