You are, of course, referring to Thomas Malthus' population theory, that like most bad ideas and theories never die, just keep changing their form or language. There are many neo-Malthusians today, particularly in various socialist movements.
That, too, but I'm actually referring to more concrete, current opinion. One is the Voluntary Human Extinction Movement..
http://www.vhemt.org/
Another example is the recent London Zoo human exhibit which portrayed humans as a "plague species".
Worldnetdaily article
I am not so sure co-Consuls really "worked" that well for the Romans. If it ever did, I am afraid it was not for very long.
As for that, we still have 250 years before our republic has lasted as long as the Roman Republic did. We sill have 200 years before we even hit the time of Sulla and Marius. We had a very bloody civil war only 70 years after the ratification of the Constitution. It was centuries before the Romans had a civil war. I'd say it worked out alright.