But first, 5 drinks in 2-3 hrs for men vs. 4 drinks in 2-3 hrs for women isn't that different. Second, women on average weigh less, so that contributes to the difference as you mentioned. And third, there are other ways alcohol affects men and women differently.
Edit: Just saw the 15 drinks/week for men vs. 8 drinks/week for women which is a larger difference. However, to call USA Today 'sexist' because of that is kind of out there. These numbers aren't just made up out of thin air: for example, http://www.icap.org/PolicyIssues/ExtremeDrinking/tabid/91/De...