A social safety net may stop some negative mutations from being selected against, but positive traits still get people laid more.
Also, why do you say 'some'? It would stop all negative mutations, as all people are given the ability to reproduce. Your argument seems to be that people with negative mutations would not be attractive, but often they are attractive to others with negative mutations themselves. Or just people who no longer breed purely based on biological fitness - again because of modern civilization.
There is definitely no contradiction there. Genes will still evolve, but it will no longer be through a process of natural finding the most positive genes. Or I'd guess you could say that we will now evolve towards genes that enable the largest families. And the largest families are predominantly in poor suburbs. The actual environment is artificial though, as those families would not be able to survive on their own without support. Taken to an extreme, it would technically be 'evolution to destruction' by selecting for negative traits that make it impossible to survive outside of the safety net. Luckily we're nowhere near that kind of extreme.
What's "positive"?
> The actual environment is artificial though, as those families would not be able to survive on their own without support.
I apologise to those who are offended by my stereotyping - If anything, I'd expect it's some of these people who are most able to survive on their own in the scenario of nuclear apocalypse and all major cities destroyed.
In such a scenario people like software engineers on HN, may even have lack the traits for survival (inherited or learned) - many of us do not know how to fix our own cars or grow our own crops.