Might as well pack it in because you have to discriminate against everybody. Your reasons not to run Horowitz's ad can be used to refuse just about all advertisements. Business ads are political by nature because they want money and attention. Public service ads are political because they want to inform readers about important topics that affect them. Some advertisements take an insulting and menacing tone to attract readers' attention.
Many ads have misleading statements.
Discrimination is never, ever a good reason to deny people a chance to have their voice heard, whether they write a letter or pay for an ad. People battled over slavery, segregation and civil rights to end discrimination. What the Stater has done is a slap in the face of what those groups fought for.