If GBL is diluted and consumed slowly, then, just like alcohol you have the chance to get your stomach pumped. If you drank lab grade ethanol, you'd only need a few mls too many and you'd be out cold from that. A few mg too much 2c-x and you're out, a G too much heroin and you're stone cold, a few too many benzos, you haven't got much time left. You got it right, drugs are dangerous, that's precisely why they need to regulated, and people need to be better educated about the risks.
Mixing drugs is inherently dangerous, and I'm shocked that someone who's been here so long thinks that only applies to GBL. Mixing drugs is one of the most dangerous things that you can do, no matter what you take. I think the real issue here is that britain's most popular legal high happens to be quite dangerous to combine with GBL. If alcohol was illegal, most people probably wouldn't bother.
GBL is not in itself particularly toxic, certainly not up there with alcohol. There is a small load on the liver converting the GHB, but from there the only metabolites are carbon dioxide and water. Alcohol has a number of toxic metabolites including aldehydes, which cause the liver terrible problems.
Prohibition is not the answer this time around.