Logotherapy and Nihilism

I happened to re-read some portions of Victor Frankl's The Doctor and the Soul: From Psychotherapy to Logotherapy recently. Despite the flaws of the book, it appears to me that Frankl makes a convincing case that the realization of values is always a possibility, and that meaning in life (not referring to the grand meaning of life) is generated by the realization of values. These values can be creative, experiential and attitudinal. These values remain within our reach even during the darkest moments, and sometimes it is in the darkest moments than an individual is able to generate some semblance of meaning in his life. Frankl, however, doesn't stop here and further maintains that we are obliged to realize these values. It is with regards to this notion of obligation that I remain unpersuaded. I may have missed it but I didn't see any argument regarding the validity of this obligation; it was only asserted, though quite emphatically.

How would a nihilist respond to the assertion that the genesis of meaning is always a possibility, at the very least through attitudinal values, even amidst great suffering? Ideally a nihilist would deny this possibility in the first place, but I am sufficiently convinced by Frankl that it is a possibility. With hands so tied up, is an answer still possible? A nihilist may undermine the validity of the attitudinal value, viewing it as a comfortable delusion (phenomenologically valid, but metaphysically unreal). He may argue that it ultimately accomplishes nothing: so what if an individual died believing that his suffering was meaningful? It doesn't change the fact that he still suffered and still died. Frankl may retort that if one is to suffer, why not suffer meaningfully, if it is possible to do so. A nihilist may reply that one may pursue such a course, but there is no obligation to do so, especially when one views such an attitude to be ultimately futile. 

To the person who has already realized attitudinal values, there is no sense of futility. But to a nihilist, who has not realized any such value, and refuses to do so even when the possibility is acknowledged, I see nothing that may oblige him to do so or make him view the attitude as worthwhile.