Two important points:
The Court did not rule that California must allow same-sex couples the right to enter into "marriage." It merely ruled that if the state allows opposite-sex couples to do so, then same-sex couples must be treated equally. The Court explicitly left open the possibility that the state could distinguish between "marriage" (as a religious institution) and "civil unions" (as a secular institution) -- i.e., that California law could leave the definition of "marriage" to religious institutions and only offer and recognize "civil unions" for legal purposes -- provides that it treated opposite-sex and same-sex couples equally. The key legal issue is equal treatment by the State as a secular matter, not defining "marriage" for religious purposes.
No rational person can criticize the Court's decision here without having at least a basic understanding of the governing California precedents. Anyone who condemns this ruling without having that understanding will be demonstrating a profound ignorance of -- and contempt for -- how the law works.