There is no way to exclude universalism
a priori. The New Testament is quite ambiguous on this issue, having passages that seem to suggest support for both Hell and universalism. Given that not a few of the brightest minds of the church have held a view open to universalism throughout church history should be enough for us to approach the issue with humility. For every quote that an eternal-Hell advocate might present, a universalist can offer a quote from the NT that strongly suggests universalism.
Moreover, the united church of the first millennium never condemned universalism. The most that ever happened on this issue was that the emperor Justinian wrote a series of anathemas against aspects of the theology of Origen. The emperor asked that the fathers of Constantinople II include his anathemas within the decrees of that ecumenical council. But, modern scholarship has concluded that the anathemas were never incorporated into that council's decrees (see Norman Tanner's editorial notes on Constantinople II in his
Decrees of the Ecumenical Councils, Georgetown University Press, 1990). So, it's likely that universalism has never been condemned in an ecumenical council.
Now, whatever are someone's personal beliefs on eschatology is a different story. Some folks are convinced of the Augustinian vision of an eternal Hell, maybe even believing that most people who have ever lived are headed there. Still others are oriented toward believing that the scriptures, theology and philosophy, when taken together, are strongly suggestive of universalism. Others opt for a "middle way," of a limited Hell with some sense of temporality/finitude intrinsic to it, with Heaven having an inequality due to how a person lived her life here (i.e., the last shall be first). And then there's the also-ran of annihilationism..
I've participated in these types of discussions many times over in the past. I know that folks get very impassioned that their particular view on eschatology must be the correct one (i.e., it's "biblical"). But, given the sheer numbers of big brains in our church's past who have disagreed with St Augustine's vision of eternal-Hell, the "openness" of the church's history on this issue, and the
recent resurgence of scholarship on this topic should be enough to force a little humility here. We all want to think we have "the truth" on this issue, but as you dig deeper and deeper, the water gets muddier and muddier.