When the Buddhists first encountered the Muslims in Central Asia and Afghanistan (remember the Bamiyan Buddhas?), the Buddhist reaction was no reaction at all. The Buddhists tamely submitted to the Muslims. No they did not embrace Islam en masse; they just gave themselves up for being slaughtered en masse by the Muslims.
Many of the Buddhists never learned to resist the Muslims. Even when the Muslims raided famous Buddhist Universities like Nalanda in India’s Bihar province, the Buddhists died en masse when the Muslim swordsmen slaughtered them like hyena would devour a clutch of rabbits in a cage.
http://www.historyofjihad.org/thailand.html?syf=contact
The case that Buddhists are peaceful and serene unless provoked by Muslims is weakened by the history of relations between Burma and Thailand, both Buddhist nations. At the time of the American Revolution the Burmese brutally sacked the Thai capital city of Ayutthaya, which caused the collapse of the kingdom and a move to a new capital, Bangkok.