"Was he actively seeking a test case?"
The cake was ordered for a private function to mark 'International Anti Homophobia Day'.
Not that it matters - the bakers would have failed the test anyway.
It's worth remembering that it's well within living memory that, not only were some businesses in Northern Ireland refusing service to Catholics because they 'kicked with the wrong foot', but politicians were actually calling for a boycott of all Catholic businesses.
Attempts to hold a function on say, a United Ireland might well lead to your home being petrol bombed (some of my family experienced this for being Catholics living in the wrong part of town)   
There were pubs in my home town of Liverpool who would refuse service to anybody thought to be Catholic or at least, you woould be quite likely to find something nasty ploating in your pint.
But, as the song says:
"These are more enlightened days, Cru#l men and savage ways we left long ago" - sort of!
Jim Carroll