On Universalism and Exclusivity

Could there be something intrinsically ecumenical about exclusivity?

"And since infinity cannot be divided by two or three or more (a mathematical fact), it follows that there cannot be one God for Jews, another for Christians, another for Muslims, another for Hindus and yet another for the godless, etcetera."

--Hassan Hathout

Hathout, (a Muslim author) argues that there can only be one God. This is a strikingly exclusive sentiment. The implication, however, is that we all worship the same God, a strikingly ecumenical sentiment.

True, exclusivity does not always contain intrinsically ecumenical sentiments. Sometimes it does, however, at least to a limited extent. Interestingly, universalism offers even fewer ecumenical possibilities.

Let's say that what each person believes is equally true. We all disagree to some extent, however, so how could each person have an equal corner on the truth? Well, what each person believes is true for them, not necessarily for you. So what I believe is true for me; what you believe is true for you; and on any point of disagreement we can therefore be equally right. But wait, if my truth is really so strictly personal, what happened to universalism? What do we actually have in common? In fact, I've concluded that the necessary relativism of extreme universalism soon becomes rather isolating, if not downright exclusive.