Partially true - if accepting altcoins will be compulsory, this idea have no difference with taxation.
But assuming that main production factor will be the capital (robots) and not the labor, no people will be force to work, just bourgeoisie forced to share production means.
Perhaps I need to clarify. No one would be forced to accept the altcoins. Just as with Bitcoin, choosing to get involved is totally voluntary. You could also trade in the coins without any obligation to accept them in the future.
But if and so long as one does choose to generate the free coins, one would be accepting an obligation to accept payments in the coin - at least up to the amount of free coins you spend. (And this is not a hard fixed rule, it's just my current thought on how it would work.)
Instead of thinking of it as "free" coins, it's better to think of it on the same model as a government (or a bank like the Fed) printing coins and putting an equal debt on their ledger. The entity - government, bank, or individual, "loans" the coins into existence. Yes, it sounds like fairy magic, but that's pretty much how US dollars work...
BTW: It's awkward to keep referring to this as "the altcoin".
Suggestions for a good name?