City of Houston subpoenas pastors' sermons, speeches, etc.

We are learning from a report by the Houston Chronicle that, in a move which clearly violates the freedom of religion, the City of Houston has subpoenaed "all speeches, presentations, or sermons related to HERO [the Houston Equal Rights Ordinance], the Petition, Mayor Annise Parker, homosexuality, or gender identity prepared by, delivered by, revised by, or approved by you [pastors] or in your possession."

The Religion News Service offers a helpful background to explain the reason for the subpoena (links original, emphases mine):

Houston has subpoenaed sermons given by local pastors who oppose an equal rights ordinance, it was revealed Tuesday (Oct. 14).

Houston Mayor Annise Parker, who drew headlines for becoming the first openly lesbian mayor of a major American city, has led support for the ordinance. The measure bans discrimination among businesses that serve the public, private employers, in housing and in city employment and city contracting.

Under the ordinance, transgender people barred access to a restroom would be able to file a discrimination complaint, one of the hotly contested parts of the ordinance.
The ordinance, which exempted religious institutions, was passed in June, though its implementation has been delayed due to legal complaints.

Opponents were hoping to repeal the ordinance through a repeal initiative, claiming the city’s attorney determined wrongly they had not gathered enough signatures to qualify for a ballot. The ordinance’s opponents reportedly gathered 50,000 signatures, well over the 17,269 needed for a November vote to repeal the measure, though proponents of the measure have questioned the validity of the signatures.

Let's presume that some of the signatures were invalid; that should be easy enough to determine. To invalidate the repeal,though, would require that more than 32,000 of the collected signatures were invalid. Is this at all likely?

When Mayor Parker first announced her anti-discrimination legislation last April, the Houston Chronicle reported her as saying:

"The Houston I know doesn't discriminate. It really doesn't matter in Houston, and it shouldn't matter in Houston, your place of origin, your gender, your age, what physical limitations you may have or who you choose to love," said Parker, the first openly gay mayor of a major American city. "It's time to codify in ordinance that position."

One might well - and rightly ask- if Houston doesn't discriminate in the first place, why is such legislation even necessary at all?

At the same time, one might well - and, again, rightly ask - isn't the City of Houston discriminating against "conservative Christian activists"? Shouldn't there be a law to protect them if the city of Houston doesn't discriminate?