The extreme Shiíte Islamic regime of the Ayatolla's in Iran for years and openly has declared its fundamental aim of destroying Israel. It ttried to do so through Hamas from Gaza; through Hezbollah from Lebanon; and through the Shiites from Yemen. Building their own nuclear weapons was to be the ultimate weapon for that purpose. The wars fought by Israel in Gaza, Lebanon and (currently) against Iran, are WARS OF SURVIVAL.
Wars are evil by definition and - as in other wars - international (humanitarian) law is disregarded. One may condemn Israel and organize demonstrations. Still one must understand the context.