Context is everything. If you were facing ISIS and al Qaeda and already half your country was under Islamist control with tens-of-thousands of Islamist foreigners fighting to transform your country into an Islamist theocracy with Saudi Arabia pulling the strings, what would you do?

Anyway the numbers are completely unverified. It's a worst-case scenario, i.e. guess. Politicized, of course, by the media and presented as a fact, which it isn't. It qualifies as fake news. Incidentally how many Syrians have been killed by the Islamist opposition/terrorists? I think the answer is hundreds-of-thousands.