Those glasses are a pragmatic solution to a moral problem, so there's not point in discussing the moral problem, and your parent is presenting a pragmatic (as depressing and curtailing to personal freedom as it is) solution in counterpoint to the glasses.
The moral problem is some people rape people who are intoxicated or who they got drunk with the intent to rape. The ideal, moral solution is people stop raping. The number of people of who rape (EDIT: and the number of rape episodes) should absolutely be reduced, but ending rape altogether isn't going to happen in our lifetimes.
So, to reduce the number of rapes we can use things like the cups (which could avoid intoxication by date rape drugs) but also try not to drink too much, especially if you don't have someone to watch out for you.
The moral problem is some people rape people who are intoxicated or who they got drunk with the intent to rape. The ideal, moral solution is people stop raping. The number of people of who rape (EDIT: and the number of rape episodes) should absolutely be reduced, but ending rape altogether isn't going to happen in our lifetimes.
So, to reduce the number of rapes we can use things like the cups (which could avoid intoxication by date rape drugs) but also try not to drink too much, especially if you don't have someone to watch out for you.