The key is in the words "by vaccination," because the term is generally used to promote immunity by vaccination. Reducing the reproduction number by that mechanism is desirable, and it is important to encourage people to get vaccinated in order to achieve herd immunity. So in the context of immunization programs, herd immunity is a good thing.

It is also the case that you can achieve herd immunity by letting people get sick and die, some of them. You also reduce the reproduction number by that method, but at a high social cost. So in the context of ruthless political manipulation, herd immunity is a bad thing.

In the case of the coronavirus, where there is no vaccine, the only way to manipulate the reproduction number is by social actions like social distancing and quarantines. One would hope that those actions are not along the lines of "let them get sick and die." I agree with that hope!

However, it seems to me that in using the words "herd immunity" to describe a cruel political strategy, one is using the words correctly in the technical sense but abusing them in the (potentially more important in the long term) overall sense.

It is not, I argue, a good idea to associate the idea of "bad" with "herd immunity," because doing so plays into the anti-vaxx strategy.