I do agree. There could be situations where the author needs to be anonymous, sensitive as the subject matter is. In fact moderators in citehr.com, where I am an occasional contributor, often advises the authors of sensitive queries to opt to be anonymous. It is my considered opinion that experts certainly have the option to offer their suggestion to anonymous queries.
Another aspect is 'repeated' queries. Most often, such repetitions are not deliberate but technical. It is my considered opinion that experts need not take an offence in such cases.
Thirdly, and perhaps more important, expertise is rather a relative term. it is my personal experience that I have learned more than I have given. Hence, it may not in the fitness of things that too much air of is made of the contribution or free service the we are rendering; it is equally important that our suggestions are restricted to the legal elements of the queries raised. It is not ideal that experts should indulge in being judgmental of the queriests.