If there's probable cause and a warrant, sure--just like there should be anywhere. But no, warrantless mass surveillance of mosques just because they're mosques would be a significantly unconstitutional overreach.
Seems like a reasonable statement.
It is, with the one caveat that sending in informants doesn't require a warrant generally. But the idea of widespread monitoring of mosques is a bad idea.
Just to be clear, I don't think anyone is advocating indiscriminate, widespread monitoring of mosques, which is both impractical and unnecessary. No, the FBI knows the dozen or so most problematic mosques in the country.
Example:
Masjed As-Saber, Oregon's largest mosque. Why the interest? Because of the following timeline:
The top 10 or 12
problematic mosques should probably be monitored, given that, as Dr. Gorka mentions, radicalization takes place via either the internet or an imam within a problem mosque. As I say, I'm fairly sure we
know which of the mosques is being used to radicalize members; we don't need to monitor
all mosques in order to greatly improve our security situation
vis-a-vis Islamic radicals.