Reply from embroidery shop banning gays

I received an email reply from Herald Embroidery in KY, USA, in regards to their banning gays in their shop. It was an unusual thing for me to do as I don't at all voice my opinion to a shop outside Australia about anything. This was an unusual circumstance though as the discrimination was so bloody blatant. The reply came from a Mathew Lombard:

We recently posted five 3" stickers on the front entrance to our shop. Two of these stickers are negative and prohibitive in their message. After some public confusion as to the meaning of one which depicted a rainbow flag, we've replaced them with a clarification. 

"While we will serve all customers who treat our place of business with respect, we reserve the right to refuse to produce promotional products that promote ideas that are not in keeping with our consciences. This includes, but is not limited to content promoting homosexuality, freemasonry, the use of foul language, and imagery which promotes immodesty." 

Thank you, 

Matthew Lombard - Owner

Make of it what you will. Personally, I dunno how a rainbow with a crossed circle on it could be interpreted in any other way than discriminatory. I also say that the term "promoting homosexuality" sounds like the gay propaganda law in Russia.

I dunno, are they allowed to discriminate like that? Wasn't there some big case over there recently about a wedding cake that the cake shop refused to make as the couple were gay? I think the cake shop got into quite a bit of strife over that one.

What then would be the case if the shop refused to serve people who "promoted" being black?