Rank has nothing to do with it.
The TSgt would have the same investigation and trial that the LtCol would, and his punishment would be according to what the convening authority dictates. Officers are dismissed. Not discharged. If dismissed, the results are pretty much the same. Enlisted personnel can be reduced in rank and retire, and still be allowed to collect retirement pay. You can retire as a E-5 believe it or not. You can not reduce an officer's rank (to my knowledge) but you sure as hell can end his career with a UCMJ article. Looking to pick up 0-4 around the 12-14 year mark? Sorry, looks like your going to have to execute your EAS. Of which, you get nothing for...of course now we're playing games of what type of crime and the severity of the offense. The most egregious cases usually end up having the the offender doing time in Leavenworth. I have yet to see large samples of senior officers committing sexual assaults and not getting the hammered for it.
Your comparison to officier/enlisted treatment wrt the UCMJ is naive and shortsighted. Sounds like the usual enlisted hate mongering towards officers.
In my service, Marine Officers would be raked over the coals twice as hard as any comparable enlisted personnel.