But, of course, as we well know there is no clear, unambiguous definition of any of these taxonomic concepts just as there is no clear definition of life. Attacking the Kind concept on the grounds that it lacks a single clear definition is hypocritical at best.
Not hypocritical. The Creationists make statements of fact about what happens in the world. They say that evolution only happens within a kind. Whenever evolution is shown to them, they say it is 'within a kind'. Without predefining what a kind is, they have an eternal intellectual hidey hole.
So the point is to show that 'evolution only happens within a kind' is a statement that asserts a fact that requires a certain level of knowledge about 'kinds' if it is to have any relevance to the debate. Clearly they lack the knowledge needed to make the statement so it is a valid criticism.
Whenever I have seen biologists talking about 'species', 'genus', 'family', etc., I tend to see different language in use. If a biologist were to make a statement about what can and cannot occur within a 'species' then we'd be right to criticise that biologist if they didn't specify what they meant by 'species', given its acknowledged ambiguity.