No. I've stated that your employer has the right to set the requirements of employment, and that you have the right to say no. As for company liability, you already stated that it was a company car and that the company requires you to travel. That makes the company liable.
Again, the biggest problem is that drug testing does not test for impairment, and in some cases, does not even test for the actual "illegal" substance.
So don't work for that employer if you don't like it. They write the checks, so they, not you, decide what is reasonable. It frankly has nothing to do with the substance being legal or illegal. Won't you get fired for having a legal amount of alcohol in your system while you're driving the company car?
The point is, it wastes billions of dollars per year with absolutely no effect on safety, and the only people who ever get caught are pot users who are not impaired in the first place. It also creates a poor work environment.
Now who's assuming? Your assumption requires us to believe that either the known consequence of termination has no effect on the decision process OR that pot users are just too responsible to ever come to work impaired. The facts are much different. Accidents due to smoking pot and/or drinking alcohol are low because employers don't tolerate it.
If you allow government to dictate what you cannot ingest, then logically they can also dicate what you can ingest, and of course then they can also dictate what you must ingest.
Hogwash. Like saying that if you let the government decide who can't vote (felons), then "they" can also dictate who can vote, and of course then they can also dictate who you must vote for. Just a nonsensical diatribe of nonsequitor logic.
...there was no drug problem when drugs were legal.
Again, hogwash. Morphine was a tremendous problem as soon as it was available. The fact is that very few drugs other than alcohol were available to anyone in the U.S. before about 1865. As soon as they became available, their irresponsible use became a problem. How exactly do you explain the issue of opium in China? Did they only imagine that there was a problem?