Additionally double male plugs are known as suicide cords
for a reason. One mistake means that you or a loved one could die.

You can hurt yourself on anything, and suicide cords are easier than many;
but are they really that dangerous?

If you opened your main breaker first, wouldn't it be perfectly safe to plug
into the backfeed outlet first and then into the generator? (yes, I know
that if you forget to open the main breaker it is potentially live...)

And if you foolishly plugged into the generator first it still wouldn't be
all that dangerous. Touching the hot alone would do nothing since the
generator is not grounded (and hopefully the genny has a GFCI anyhow). To
be hurt it would be necessary to touch both hot and neutral. While that
would hurt, unless it was on the chest (a difficult thing to achieve) it
wouldn't be particularly dangerous.

I know 10 people will jump on this and tell me that everyone know they are
really dangerous and I am fool to be questioning it; but HOW are they really
dangerous?