The strongest objection to interpreting Kierkegaard's leap of faith as a manifestation of relativism comes from the simple fact that Christians express very strong preferences and articulate a powerful basis for those preferences.
Relativism can be many things, but I think for many Evangelicals it comes down to "everything is just as good (or as bad) as anything else." There is no justification external to an individual for preferring one thing, one set of beliefs, one religion, etc., over another.
One way of dealing with this perceived lack of values and bases for preferences is to latch on to one and hang on to it for dear life. The relativist, as I describe him, believes there is no basis to preferring one set of values over another. Consequently, for him, the choice is completely arbitrary.
I think the reason Evangelical Christianity has such a following is simply that it preaches that without God there is no alternative. Once one has achieved belief, then the demon of despair and of uncertainty is exorcised.
To make matters worse there is a perverse logic at work: the perceived lack of foundations without God becomes proof of the necessity of some kind of belief. The alternative to belief as taught by Evangelicals is nothingness, despair, and a plethora of choices.
For all the apparent absurdity and rape of reason that Evangelical theology appears to be, there is a clumsy sign language of experiences to be interpreted.