Everyone is welcome at a UU church.  There is no litmus test to become affiliated with one of our congregations.  However, as with any relationship, our experience has been that the more your values align with ours, the better the fit between you and UUism.  If you have a strong opposition to one of our values, you may begin to feel it is a burden over time.
Quote from the Article II Study Commission:
"Article II is the purpose of the Association and commitments of its member congregations to each other. It should inform our congregational and associational life, but is not written to be a personal code or set of commitments.
The Freedom of Belief clause expressly prohibits any creedal test of membership in our congregations. While these are our shared values, no one must swear or attest to them to become a member."