Although recognized as a legitimate sect of mages, the Thanatai suffer a very negative reputation for their research and practices. While they may be as scholarly or influential as they please, no ethical person would favor their ability to raise the dead.
The Thanatai, however, are a reserved and pragmatic sect. If the soul disappears upon death, they ask, then what use is there for the empty shell that it once called a body? The Thanatai thus see corpses as tools -- discarded husks that are obviously no longer needed by their owners. The undead that they raise are quite easily put to work as servants, valets, or even fodder for the outraged mobs that seek their destruction.
In their studies of death and its circumstances, the Thanatai have learned much beyond the raising of corpses as well. They have learned to replicate the aspects of death in beings, and they have learned magics that steal life and breath to sustain their own aging bodies. Their greatest achievement, however, lies in searching the barrier that falls between the tangible world and the abyssal void... and acquiring a sight that allows them to catch glimpses of future events.
Regardless of their achievements, the Thanatai are almost universally hunted and executed across Antaria. Their persecution has forced their mages to hide among the populace, and to take refuge in isolated strongholds for their own protection. Very few Thanatai live in the open, and those who do so are constantly suspected of the most vile crimes.
The Thanatai themselves remain reserved and pragmatic. In their own way, they have realized more of the forces around them. If their peers would choose to reject their findings on the basis of stereotypical belief, then perhaps they were not worthy of such knowledge in the first place.