Keg Smash Taunt?

477 Blood DK here. I can hold aggro against anyone and everyone tanks included of any ilvl 99% of the time but when a BM Monk uses keg smash they rip aggro like they are taunting. This has happened 100% of the time anywhere from 440 ilvl to 470 ilvl BM Monks. Is it broken or is this by design? I have asked many friends who play monk and they say it is definitely not a taunt yet it rips aggro more than a 480 DH. Please advise on how to deal with this other than just not tanking with BM Monks.