Just to followup on this thread, I've come up with a satisfactory solution
to my problem.

I was overstating the case when I described the defrosted carrots as black;
they were a little darker and softer looking than before the freezing but
black is too strong a word. So, when the third bag of carrots defrosted, I
decided to try a bite of one of the carrots. I figured one bite wouldn't
kill me, especially if I spit it out if the taste were off.

As it turns out, the carrots tasted fine. They were soft and absolutely
saturated with moisture; it was as if they'd been soaking in water for
hours. I think that explains the colour change. But the taste was fine and
I've eaten a fair number of them now with no ill effect.

And for what it's worth, I didn't put the carrots in the freezer because I
was drunk. In fact, I don't drink alcohol (or use illicit drugs). I have
been in the habit of buying only frozen vegetables for a long time so I
inevitably put vegetables into the freezer when I was done with them,
without even consciously thinking about it.

The correct solution to my problem was, as several of you pointed out, to
simply stop putting the carrots in the freezer. However, since I was not
consciously deciding to put them in the freezer, I had to think of another
solution. I've decided that future packages of baby carrots will be
immediately transferred to an empty margarine container as soon as I unpack
my groceries. That way, I will be very unlikely to ever put them in the
freezer because they won't be in a bag any more and because I don't put
margarine in the freezer. Simple, but it should work ;-)

Rhino