It's complicated and the implications and scope are not entirely clear.

The court stated that creative works such as web design qualify as a form of speech, and that the first amendment does not allow the government to use law to force creators to speak any message — especially one with which they disagree. Essentially, any business with something that might be considered speech as its product or service may be free to discriminate against protected classes. We aren't sure how far this will extend in practice, but I expect many will test it.

In this case of this post, it depends on what is being sold.

Edit: wrote this before my coffee and thus neglected to point out what replies said: political affiliation is not a protected class in America and these signs are a bit misleading. See replies.

I am not a lawyer.

These signs are surely in response to the recent US Supreme Court ruling which allowed a website designer to refuse to make websites for same-sex weddings.

First, churches are religious; Trump supporters are political, and not religious. In the US, religion is a "protected class", but political alignment is not. But traditionally, political alignment or part affiliation is not discriminated against, even if it is federall legal to do so. (Various states may have their own clauses making political alignment a protected class in certain contexts, I'm not sure.) Also important to this discussion is that sexual preference is not a protected class federally, although I know that many states have enshrined protection for sexual preference in their own state laws.

If a case were brought about discrimination against Trump supporters because of these signs, in a jurisdiction where politics was not a protected class, I should expect that that case would fail, under current law. But just like SCOTUS is highly political right now, lower courts are, too, especially lower federal courts. It's anybody's guess as to whether a given judge would actually adhere to existing case law.

For the religious side of these signs, it gets interesting. As above, SCOTUS has ruled that a religious business owner can discriminate against customers based on the business owner's "religious disagreement" with a position held by the customer, presumably where that disagreement does not overlap with a protected class.

And there's the rub. Religion is a protected class, so it should be prohibited to discriminate against someone for their religious position. This, however, really tips the scales in favor of the religious: the religious business owner can discriminate on the basis of their own religious belief, but no one can discriminate against them because of that same religious belief. To me, this seems to tread very heavily on the Establishment Clause of the First Amendment of the US Constitution:

Congress shall make no law respecting an establishment of religion ...

"Congress," in this context, has been interpreted by the courts to mean more generally "the government," at any level. The recent SCOTUS ruling gives a religious business owner the right to discriminate on the basis of their religion, but the right of other people to discriminate against that business owner on the exact same basis remains prohibited. Again, I am not a lawyer, but that seems to be clearly in opposition to the Establishment Clause.

All of this is interesting, but none of it is cause for concern.

What is cause for concern is the foundation of Obergefell, which made same sex marriage legal in all of the US. That basis is that the only difference between opposite sex and same sex marriages is the sex of one of the people in the couple. An argument I recall from the time was that prohibiting same sex marriage is unconstitutional, because to do so would be discriminating against someone on the basis of sex - which is a protected class. However, that does not appear to have been mentioned in the court's ruling.

No matter the reason, if it is unconstitutional to discriminate against same sex couples in the context of their getting married in the first place, it should stand to reason that it would be unconstitutional to discriminate against those same sex couples in any other context. Reason does not appear to be this court's strong suit; they have decided that the rights of religious people to discriminate on the basis of their personal and individual beliefs "trumps" (pun intended) the rights of people (religious or not) to not be discriminated against.

This is a "canary in a coal mine" to overturn all manner of previous courts' rulings: Obergefell (same sex marriage), Loving v Virginia (interracial marriage), Griswold (access to contraception), Lawrence v Texas (legalization of homosexuality), and certainly others.

Again, all of this seems to prioritize religion, which is in clear opposition of the Establishment Clause.

Political affiliation is not a protected class. You are permitted to discriminate based on politics. Religious affiliation is a protected class. You cannot discriminate solely on the basis of religion... Until now.

Conservatives love to discriminate, but their new rulings are also making it easier to discriminate against them.