Kingsley didn't know how much Terrence knew about the potion or could say. First of all, they didn't know how much Death Eaters were informed. Secondly, the man was an Unspeakable, so anything going on there was off the table - loyalties or no. Creativity could only help so much.
The tips Terrence suggested were interesting, as neither had happened in Kingsley's case. He had simply...figured it out on his own. And the risks had been too great to get actively involved in other people coming clear most the past few years. Of course, Kingsley hadn't known what was keeping people under the influence, and that made acting too soon far too risky. It was unfortunate for those he watched, but he had kept close tabs anyway. Not to mention, hopefully they wouldn't need to emotionally traumatize everyone they brought off. It sort of injured the person and made them of limited use.
"We need to be able to control or help them effectively," Kingsley replied, "If the government takes any large action, they will be defenseless." If the government didn't know who to blame, it struck at those it could. Kingsley hadn't known those who were killed and blamed for the attack at the Ministry very well, but they hadn't been associated but loosely at best.
"I do not know who is responsible for the attacks on families," Kingsley's eyes grew harder, "but I do not approve, and I do not fight like Death Eaters do." That was what those actions were. If they killed innocents purposely to win, then they were no better. There was no point in winning.