I believe the simple answer to the OP's question would be that no, most UCC members wouldn't be uncomfortable with the denomination's stance. If they were and felt strongly about the issue, there are plenty of other churches they could join.
Although I'm not UCC myself, I would feel just as comfortable being a member of the UCC as I am the PCUSA, and in fact when I move, I plan to check out churches of both denominations. I think I'm close enough to the UCC to respond to this; but what got lost somewhere along the way is the fact that the original question was addressed to UCC members, not to anyone who happens to have an opinion on abortion.
The initial question, baited as it may be, doesn't break the debating rules, but basically everything after that does. It's no different than if we UCC and UCC-supporter types went into the conservative areas to debate abortion. Heck, even though the Presbyterian forum is technically open to liberal as well as conservative Presbyterians, I'm not going to go there to debate issues like this, since I don't care to stir up unnecessary drama (which seemed to be the only purpose of this thread).