If we read your question carefully, the answer is clearly Yes.
You ask, "Can a population of humans who evolved to be utter morons survive to this day"
Well, if they evolved to be utter morons then clearly that was an adaptive strategy for them at some time and some place.
Therefore your current question boils down to "Can a species of morons survive today."
Since you have asserted that there was a period of time during which they survived, then clearly they would be able to live in a similar environment today - provided that environment was available to them. This could be natural or artificial.
Really the "today" part of your question is irrelevant. The real question is "Is there any environment in which a species would evolve to become morons?"
With that in mind I will interpret your question to mean:
Is there any environment in which a species would evolve to become morons?
and try to answer that.
I think the only answer is selective breeding. Aliens or other humans would observe your species and note which individuals were most moronic. They would then breed them together to 'improve' the line. Instead of eugenics they would be practising dysgenics.
They would of course have to provide a protective environment for these creatures (isolation and padded cells for instance) to prevent them from harming themselves and others. Breeding might have to occur through artificial insemination.
If you think humans are incapable of such a stupid breeding scheme then just look at what we have done with some animals. There are dog breeds that are incapable of copulating naturally and have to be helped, some cannot give birth naturally and have to have Caesarian section as a matter of course. There are extraordinary fish varieties that would not last a day in the wild, so distorted are their features.
One Vet's Opinion: Why Do We Breed Dogs Who Can't Give Birth