The mission of facilitating spiritual growth gets captured by special interests who want to use the organizational resources to advocate for social justice causes that are peripheral to the prime mission and vision of the organization. This organizing around social justice issues cannot sustain a mature organization because the motivations are situational and relatively short lived.
David Markham, Book Notes on The Gadfly Papers by Todd Eklof
Unitarian Univeralist congregations are not social justice agencies. UU churches are not social activist organizations. Social justice and social activism organizing is best left to the professionals. The mission of Unitarian Universalism is to provide covenantal relationships where spiritual growth and development an be facilitated.
If this spiritual growth and development can be facilitated by corporal works of compassion and mercy social justice work can be a vehicle to nourish such spiritual development. However, social justice work is not the purpose of UU churches itself but a means to another end which is to raise the consciousness of people engaged in the work and those with whom they interact.