Just watched the Dual Survival 3, "Meltdown" episode. In the beginning Cody and Joe have found a backpack in the African desert, where they are stranded this time, with some semi-random stuff, including a couple of full beer cans. They both argued that beer (24 oz of precious water! and also a great source of calories!) must be discarded immediately, as alcohol is diuretic and would only help with dehydration. Isn't that just a plain stupid move in the dry desert?

In fact, it seems to me, that this show is too often becoming quite misleading. In the same episode, Joe is bravely walking over the chest deep creek, which is possibly infested with alligators, instead of simply swimming on the surface, which is almost 100% safe in such rivers, as crocs are watching for animal legs.

Diuretic which I think we can agree is a bad thing in the desert where (actual) water may be hard to find.

So I agree with Cody & Joe, dump the beer. The calories are minimal and will not offset the loss of water.

There is "actual" water in the beer. Even if the alcohol in it (which is a very little amount in the beer) will cause more frequent urination, in a desert survival situation that water (urine) must be collected and re-used anyway.

For the calories, you are wrong, each beer can is more than 150 calories, that's about 2 large eggs each!

Also, I can easily google articles calling strong diuretic properties of beer just urban myth: http://www.socialanxietysupport.com/forum/f24/coffee-and-beer-cause-dehydration-a-myth-22964/
and
http://www.dshack.net/2011/11/no-coffee-doesnt-dehydrate-you-and-neither-does-beer.html

The last one shows a simple math of intake and diuretic release, so even if they don't collect urine (which is nonsense in the given situation) they could still benefit from the beer water intake.

Question, If you heated the beer would the alcohol evaporate first leaving most of the water and calories?

Good one.
That's how the nonalcoholic beer was made in the past: http://gizmodo.com/the-science-of-non-alcoholic-beer-509674407
In short, beer boils at lower temp. than water, so all what Cody and Joe had to do is to bring it to the boiling point for a second or two.

By the way, calories in various beer: http://www.fitsugar.com/Calories-Popular-Beers-1504697

Sierra Nevada Bigfoot 330 cal!

First, not all beer is the same; some have a lot more calories (carbohydrates) than others. "Liquid Bread" was the term I learned when I was stationed in Germany. It referred to German brews, not US "lawn mowing" beer. So, In part, depends what type of beer it is.

Second, even with low carb beer, I don't think the intake of, say 12 US oz of fluid + at least some carbs, will cause you to lose more than 12 oz of liquid, so it is a net gain in liquid.

Heck yes, 1 beer each will help: now, a six pack all at once is a different question.

I'd boil it! That won't get all the alcohol out; alcohol is extremely hydrophilic, you need a centrifuge or molecular distillation to get all of it out. But boiling briefly will get most of it out. Lots of calories and a lot of water, don't waste it!

I think Alex and Phaedrus are right, even if you didn't try to boil off some of the alcohol the beer would provide a net gain in water. Plus those complex carbs are golden in a survival situation. Regarding the carbs, they are even more important in the desert because when you digest carbs, there is a net release of free water that becomes available to the body. Protein digestion uses water in order to flush the tissues of the resulting ammonia while carb digestion provides more water to the body. Here is an excerpt on the topic from Golden & Tipton's excellent book which unfortunately costs a lot more in print than it used to.

Regarding caffeine & diuresis, IIRC much of the diuretic effect happens to people who don't regularly consume caffeine. Those who have caffeine regularly have less response to the mild diuretic effect.

You should regard the info in show as good survival info if you are determined to die early.
For the beer it really depends on the actual beer. There is thin watery brew with severely reduced alcohol content, which may be OK to drink (you might not wish to actually do it as it tastes awful). And there is German Doppelbock. That has enough carbohydrates to glue a seat to your backside (if it does not, it´s too thin and the brewer will be shamed). It has enough alcohol to make you stay put. The stuff in between it outright dangerous. It make ideas look brighter than they are. They impair your judgement but leave you capable of acting stupid.
It would be really stupid to haul the beer and then not drink it. So it´s the right decision to act while they still can think clearly.

In a survival situation I can't see discarding the beers. As others have said, I'd take the benefit of the calories and water content over any, likely negligible, negative affects the low amount of alcohol might provide.