The discrimination against businesses that wish to decline business with which they disagree, as observed in European nations that have already passed these laws.
Real world examples today:
* Churches forced to stop renting out facilities to weddings after refusing to rent out the facility to a same sex civil union. Yet they'd have the right to refuse service if Muslims or Buddhists wished to rent the space.
* A Christian counselor in training, who was black, was denied her degree after referring a same-sex couple that came in for relationship counseling. She said she could not in conscience counsel them, so she referred them to someone who could counsel them without violating their rights. She received a cash settlement from the school, but not a degree. Yet she would have been doing them a disservice for counseling them half-heartedly.
* Photographers sued for declining to photograph same sex couple unions and bakeries sued for not giving civil union cakes - and forced to pay money for discrimination. Yet a black owned bakery that declined to do business with whites wouldn't be sued OR face civil penalties.
Giving homosexuals equal legal protections for "marriage" leads to legal abuse of those who oppose it for religious reasons, as we have already seen in the US and Europe. There are even religious leaders in Northern Europe and elsewhere seeing their freedom of religion and speech denied under "hate speech" laws for saying what their religions have said for 2000 years.