What was the concerning aspect of Vice President Vance's speech according to a Republican adviser?

According to a Republican adviser mentioned in the clip, while many were focused on how the speech was embarrassing, out of touch, and selling out Ukrainians, there was actually a deeper and darker element to it. The adviser pointed out that Vance was talking about 'the enemy within,' which uses language reminiscent of what Hitler used to justify the Holocaust. This alarming rhetoric suggests dangerous historical parallels that go beyond policy disagreements, pointing to a concerning rhetorical pattern that evokes some of history's darkest moments.