Drugging someone with the intent of incapacitating them and then having sex with them while they are unable to consent is unambiguously sexual assault. This isn't a grey area. And drug-facilitated sexual assault is not especially modern, either; it's a standard technique of many serial rapists.
In 1996, the U.S. Congress passed the Drug-Induced Rape Prevention and Punishment Act (an amendment to the Controlled Substances Act). This set penalties of up to 20 years in federal prison plus fines for anyone convicted of committing a rape or other violent crime after giving the victim a controlled substance without the victim's knowledge or consent. There are also various state laws that make drug/alcohol-facilitated sexual assaults felonies.
Again: not a gray area. Not a new crime in the eyes of the law.
But to see some men wring their hands in social media now that Bill Cosby has been charged with sexual assault, you'd think this was all new! And OMG what is going on? HOW CAN A MAN BE A MAN WHEN THE WORLD HAS GONE CRAZY?
Look. The percentage of my friends (mostly women but a nontrivial number of men) who have been sexually assaulted is disturbingly high. When I was 18, I found out 100% of my close friends and female relatives had suffered some kind of sexual assault. Not some. Not a lot. All of them. None felt comfortable reporting the assaults to the police or even their own parents because of the level of victim-shaming and blaming they'd have to endure.
The number of my male friends over the years who have been arrested for rape as the result of a false or honest accusation? Zero. Which is not shocking, since (1) I don't like rapists, and (2) RAINN statistics show that only about 2% of rapes result in the rapists spending even a single day in jail. Rapists are a ridiculously protected group when you look at the social pressures put on sexual assault victims to just keep silent.
So, if are looking at the news about Cosby and your gut reaction, your main thought, is not to marvel in horror that a serial rapist was lauded as a cultural hero and moral authority for decades but is instead to worry that maybe you're going to be arrested on rape charges because it happened to him ... that tells me that you've been acting like a rapist. Stop it, goddamn you. Stop hurting people.