If a viewpoint is in the majority, then it should be easy to substantiate it with reference to commonly accepted reference texts;
If a viewpoint is held by a significant minority, then it should be easy to name prominent adherents;
If a viewpoint is held by an extremely small (or vastly limited) minority, it does not belong in Wikipedia regardless of whether it is true or not and regardless of whether you can prove it or not, except perhaps in some ancillary article.