Not basically, he *was* plotting to kill him. That is the whole premise of this comic.
Yeonjo literally seduces and tries to make him lower his defences so that he may end up killing him. And he succeeds spectacularly in the first half, but ends up unable to complete the second half, even when the governor literally lays back and let's him strangle him.
The reason why many readers judge Hee-ryang so negatively (besides the obvious fact of him being a ruthless murder who killed Yeonjo's family) is because of what happened after all that. When Yeonjo, hating himself for not being able to complete his revenge and for loving Hee-ryang, and knowing that Hee-ryang loves him back, begins hurting himself out of self-hate and spite, to punish himself and Hee-ryang. And the governor unfortunately responds to that in a very military-y, very cold and practical sort of way, first, by confining him, and, currently, by blackmailing him. He went about it very poorly. But, indeed, like you said, very much like you would expect of a person with bis background. But yeah, that's why many readers have beef with him.
seme is so down baaad for yeonjo. yes, he is an ass but it actually makes sense??
he is a governor with a military background, so cruelty comes naturally to him. yet he still tolerates uke, even after the uke was basically plotting to kill him