There's a dilemma here which is present in teaching a lot of skills: do you want your hypothetical students to be building useful things quickly, or do you want them to be internalising concepts that will last them a lifetime?
If it's the former, just give people a solvable problem and let them pick their own tools. If it's the latter, start them off with some verbose compiled unforgiving strongly-typed beast like C or Java. They're best learnt in a training environment rather than on the fly, so if you have a training environment, it makes sense to learn them there. It's easier to go from, say, Java to Python than it is to go in the other direction.
At times I've thought the same myself, but I've read accounts from at least two different CS professors who said that student outcomes improved dramatically when switching from statically typed languages to Python as a first language. I suspect Python works well because it makes it easy to introduce just a few concepts at a time.
I started with Python and I didn't have any trouble learning statically typed languages.
Learning to program in a given language requires a non-trivial amount of time. This seems to be agreed upon as a good use of LessWrongers' time.
Each language may be more useful than others for particular purposes. However, like e.g. the choice of donation to a particular charity, we shouldn't expect the trade-offs of focusing on one versus another not to exist.
Suppose I know nothing about programming... And I want to make a choice about what language to pick up beyond merely what sounds cool at the time. In short I would want to spend my five minutes on the problem before jumping to a solution.
As an example of the dilemma, if I spend my time learning Scheme or Lisp, I will gain a particular kind of skill. It won't be a very directly marketable one, but it could (in theory) make me a better programmer. "Code as lists" is a powerful perspective -- and Eric S. Raymond recommends learning Lisp for this reason.
Forth (or any similar concatenative language) presents a different yet similarly powerful perspective, one which encourages extreme factorization and use of small well-considered definitions of words for frequently reused concepts.
Python encourages object oriented thinking and explicit declaration. Ruby is object oriented and complexity-hiding to the point of being almost magical.
C teaches functions and varying abstraction levels. Javascript is more about the high level abstractions.
If a newbie programmer focuses on any of these they will come out of it a different kind of programmer. If a competent programmer avoids one of these things they will avoid different kinds of costs as well as different kinds of benefits.
Is it better to focus on one path, avoiding contamination from others?
Is it better to explore several simultaneously, to make sure you don't miss the best parts?
Which one results in converting time to dollars the most quickly?
Which one most reliably converts you to a higher value programmer over a longer period of time?
What other caveats are there?