Leviticus 20:13
ESV - 13 If a man lies with a male as with a woman, both of them have committed an abomination; they shall surely be put to death; their blood is upon them.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Saying "homosexuality is no greater sin than any other." - is a misleading broad generalization. Jesus said a millstone tied to the neck of a person who corrupts children (paraphrasing) is suitable punishment, implying it's a worse sin than others.
That said, it's a slippery slope to try to rank sins by severity!
Also, saying "homosexuality is no greater sin than any other" , then shouldn't the people that deny selling flowers or making cakes for homosexual weddings deny someone that has murdered, lied, committed adultery,etc. deny them also.