There was a shock of surprise to hear that Cass was just as pressured, however, that wouldn't do to his righteous anger; and even as Cass continued, Montague quickly coming up with his own excuses, other reasons behind the money... He'd have lost his family, his mother, sister, brother- He would have been subjected as an outcast by those he cared the most about... and he'd had some agreeance with the ideals- wizards and witches were better then muggles. Muggles had no magic, they lived in ignorance and clung to their sciences that explained nothing- he couldn't respect a people that did that.
He hadn't wanted to kill though, nor did he believe a half-blood was any worse off then a pureblood. Genetics and personal experience had proved to him that. His daughters, his son, they would marry purebloods- but only to keep the line going, to keep his mother and father happy. As he'd made claims to time and again, it was their children that mattered to him, nothing more.
But now wasn't a time for nitpicking of social ideals...
"And now I am! How is your decision affecting my life?! You made a decision based on your family! That's expected!" Montague yelled, "who threatened you NOW?!" No one, it sounded like. He broke the bounds of their house for nothing, for no apparent reason but guilt over his own decision and it was pathetic.
When Vaisey asked what he was doing, Montague's jaw clenched tightly as he looked straight at him. "I can't trust you. Why the bloody hell would I tell you?" His divided loyalties were not under consideration, who knew who Cass would tell. Was he still under threat of Roldophus? Was he under Umbridge's "reign"? He had no way of knowing and would not tell of his spying when for one, McGonagall was still comatose; and he could not trust Cass to not blab it to the wrong person.