I believe that some socially liberal people should seek out nondenominational churches. I think that it is something that might be beneficial for them since their beliefs and ideals might be better suited for it. I think that some people though shouldn't be afraid to seek out more traditional churches.
Yes, socially liberal people should seek out nondenominational churches, because nondenominational churches are more likely to be welcoming to socially liberal people. People who are socially liberal might have a hard time fitting in at certain types of churches. Some churches are not shy about their conservative teachings, and can be outright mean to people who disagree with them.
While it's true that most organized religion today seems to be pushing social liberals away, people should not have to leave a faith because of that. For example, I identify as Catholic, and am having a difficult time with the Church's position on many social issues. I considered going elsewhere, but I shouldn't have to.
I don't think socially liberal people "should" seek out nondenominational churches. They can if they want to but there is no reason that they need to go to church. They can go to any church they want to go to, or they can choose to not go to any church at all.
No, socially liberal people should not only seek out nondenominational churches, because socially liberally people are welcome at a lot of church. The Bible is unclear whether Jesus was socially liberal or not. There is room for debate, but what is not debatable is that all people are and should be welcome at whatever kind of church they choose.