it's not boxing gloves that cause more head trauma, it's boxing that causes more head trauma. The matches go on much longer than mma matches (championship bout lasts 36 mins in boxing, 25 in MMA). Also the main target and concentration of damage is to the head (and partly the body). For MMA, it's a lot more spread out between the head, legs and body; because there are kicks involved. A lot more clinching and groundwork too in MMA, so there's a lot more periods of rest/nonaction.
Lastly, boxing gloves have padding. padding reduces the impact of your punch. That is why you spar in gym with 16 oz gloves (with your training partners for safety), and in competition you fight with 10 or 12 oz (less padding = more damage). Extrapolate that to MMA gloves which have even less padding.
I think it's hopeless explaining this to ppl that don't work out, but i thought i might as well chime in.