I think most people are referring to a specific case in Ireland. The bakery was refused to provide a cake with a slogan "Support Gay Marriage", citing religious objections to the practice. The bakery lost the case, and the appeal: http://www.bbc.com/news/uk-northern-ireland-37748681.

it's actually happened quite a few times in the USA as well. If you search "USA christian bakery" there's at least 3 or 4 separate cases of bakeries that have been sued on the front page alone.

[edit] by search, I mean on Google rather than HN