Nowadays practicing ones Religious Freedom can be considered discrimination in Houston the mayor demanded the sermons from pastors who disagreed with lgtbq ordinance. She considered that disagreement to be discrimination. In Iowa 2 churches are suing the Iowa Civil Rights Commission. The Commission considers sermons preached against lgbtq to be discrimination and are using govt to restrict pastors sermons. That tells me discrimination is vague and can be used to silence religious speech in churches
Erika, the only reference I can find to a Houston mayor subpoenaing sermons happened in 2014 and was concerning a legal issue. The subponeas were withdrawn within two weeks. http://www.huffingtonpost.com/2014/10/29/houston-mayor-sermon-subpoenas_n_6070650.html
The only Iowa case I can find is in regards to a brochure (poorly) written by the Iowa Civil Rights commission. The brochure has been changed http://www.lgbtqnation.com/2016/07/iowa-church-sues-change-lgbtq-civil-rights-brochure/
Is this what you are talking about?