Technically he didn't. If you care about reality, you'd know he successfully negotiated the release of the embassy hostages. Iran decided to be dicks and release them the moment he was out of office. Reagan had nothing to do with their release.
No one disagrees that Iran's regime is evil shit and murderous to its own people. My guess is Germany is celebrating their tax dollars and blood aren't being spent to eliminate it like the American rubes. If Bibi wanted regime change, he can do it. It's not our job, man.
