Your scenarios of businesses of "pro-homosexual speakers" and sculptures are simply not analogous to anything related to public accommodations laws.
Briefly: Phillips claims that CADA compels speech, in violation of the First Amendment. But CADA literally says nothing about speech; it regulates conduct. CADA does not compel Phillips to either speak or host the government's message. Phillips claims that CADA compels him to speak a celebratory message about the marriage of same-sex couples or about same-sex marriage. But the law does not achieve that effect. As the Colorado court explained, Phillips remains free to express his views about same-sex marriage. Moreover, the idea that someone who sees one of Phillips' cakes will somehow understand it as Phillips' message celebrating same-sex marriage (or a particular marriage between a same-sex couple) is patently absurd: in the unlikely case that anyone would even know who baked the cake, people do not attribute a celebratory message to the baker. If any celebratory message is inferred from a wedding cake, the message is assumed to be that of the purchaser of the cake, not the baker (unless they are the same person).
Even if it were true that baking and selling wedding cakes is something other than what public accommodations laws refer to as “goods [and] services,” i.e., even if it were true that baking and selling wedding cakes are expressive activities such as generally protected by the First Amendment, that doesn't mean that the government cannot regulate such activity. If a law that burdens expressive activity meets the requirements of strict scrutiny, it's a constitutional law. The government regulates many forms of speech and expression. The requirements of strict scrutiny are that a law has a compelling governmental purpose, is narrowly tailored and is the least restrictive means for achieving that compelling governmental purpose. The anti-discrimination provisions of public accommodations laws have repeatedly been held to have a compelling governmental purpose--see
Roberts v. Jaycees (e.g., “. . . the State's strong historical commitment to eliminating discrimination and assuring its citizens equal access to publicly available goods and services . . . which is unrelated to the suppression of expression, plainly serves compelling state interests of the highest order.”). In pertaining to only businesses open to the public, and specifically exempting “places principally used for religious purposes,” CADA is narrowly tailored; and it's difficult to imagine a less restrictive way to achieve the desired goal than outlawing discrimination in the offerings of public goods and services. CADA fulfills the demands of strict scrutiny stipulated in the case law.