You could point out that rolling back the HHS mandate does not deny them birth control coverage. Employers are still free to offer it, and probably many will continue to do so.
Rolling back the HHS mandate does not dictate anything. What it does is stop dictating something it was dictating under the mandate.
Rolling back the HHS mandate is not exempting Catholics from the law. It is changing the law, which is someone anyone has the right to petition for - for religious reasons or for no reason at all. The fact that your objection to the HHS mandate is religiously based should not disqualify you from exercising a right that everyone else has when they want to push their notions of the law should be, and no one challenges them on their motivations.
You are barking up the wrong tree in this debate. The point is not to prove the correctness of your opinion and how it is based in religion. It is enough just to prove you have the right to assert your opinion, regardless of where that opinion came from.
You could point out that Sharia Law has lots of mandates. This latest action removes a mandate. So if anything, the repeal is more like and “anti-Sharia” action.