They're doing it to help them win elections. They do it to embolden their followers: every little right they take away from a minority group is worth another small bump in the polls for them. It's despicable.
Essentially, they're re-enacting that centuries-old game of blame just to keep themselves in power. When they do things like this to us, their followers look at it and see them going after "the enemy", persecuting the people who have challenged their old ways of thinking. It's not just that they hate us, it's that they need someone to hate. They needed a rallying cry, and we're an easy target. Do any of us truly believe they'll stop there? We're in danger of losing basic rights every time they need a boost in popularity, this won't be the end of it.
Pointing that out isn't "fearmongering", it's calling attention to problems that we, as a community, will face if things don't change soon. If we can't get them out of power, then the next time they go after our rights, it's going to be a lot scarier than this.