I know this is the weirdest question ever but... can someone use hand sanitizer with 70% ethyl alcohol to wipe themselves with after a bowel movement ?

Yes and no: Well, yes, you can use it in that area. However, you may not like how the area feels after you do it. Not sure what you are trying to treat but there is likely a much more humane way of treating yourself.

Wiping with alcohol: The answer is yes. In a pinch, in a particularly messy situation, this will do fine. For routine use you would want a fabric moistened with a gentler moisturizes as in the commercial products. 70% ethyl alchol is pretty irritating and drying with repeated use.