There are actually several pretty good evolutionary arguments against continued human evolution in advanced societies.
A couple:
1. We modify the environment to suit us, removing the pressure for us to adapt to the environment.
2. In modern societies, those who are least successful in that society’s terms tend to reproduce at a much higher rate than those who are most successful. If anything, this may be an example of anti-evolution. It’s difficult to envision this not having some impact over many generations.
I wouldn't try to stretch this argument too far.
The percentage of humans in a a high-tech environment is still not a majority. When you throw in full access to modern medicines that percentage drops considerably.
Part of evolution relies on diversity within a genome. I think what we are doing currently is stretching that range by allowing some who would not ordinarily survive in a primitive cultural state to do so.
If and when conditions change, having the widest range of variation will be beneficial as that increases the odds that at least some within the population will be adequately adapted and hence will survive.
Finally, your analogy to modern societies--what makes you think that those who are "the least successful" are not well adapted? Reproducing and having large families is a primary index of success in evolutionary terms. It is the ones who are highly successful who choose to have no children that are evolutionary dead ends.
We also are able to keep even very ill people alive long enough for them to reproduce. I don't think there is any such thing as anti-evolution though. What you call anti-evolution is just plain old evolution.