It is not. That is a myth from 1950s shoddy research, that somehow keeps being repeated.
That's why people can drink it to survive when necessary.
But you shouldn’t do it even then. Your body uses it to get rid of salt and toxins, worsening the situation often, if you are dehydrated and have a weakened immune system.
Even the astronauts do it.
They filter/separate out the bad stuff, though. And they get the water from everywhere, including urine, but also shower water, sweat and breath vapor from the air (93% efficient).
