Even if I were to completely ignore the subjectivity challenge inherent in Sola Scriptura, that is, that in appealing to Scripture, each individual is appealing to his own interpretation of them (or to that of another individual's, which the person accepts derivatively) we absolutely cannot avoid the problem articulated by Fred Noltie. Read it. Read it all. The Reformed don't feel the problem right away; I'll leave you to do some soul-searching for the reasons. I digress.
Dogmatic relativism is a necessity, if the inability to form consensus on the content of revelation persists, and conceiving of the "Church" invisibly accomplishes that goal. But it fuels the further problem of knowing specifically the content of revelation. If the Catholic Church's dogma and authority is indentifiable (and asserted to be wrong, incidentally) the realization comes that all communities formed at the Reformation diverge from the Catholic Church at different places (and with each other). The obvious conclusion is that they cannot all be right in the same way at the same time. To suggest that they could is this relativism. The challenge is this: Why should I believe anything if I cannot be certain it came from God, and thus, is infallibly certain?
Here is the funny/sad part: You hear "tribalism" on the tongues of many Reformed evangelicals today, whether they got it from Dr. Anthony Bradley or not. But given the interpretive chaos of Sola Scriptura, isn't the "tribalism" objection tantamount to saying, "You refuse to relativize dogma in the same way I do"?