The constant GOP refrain that raising taxes on the rich is “class warfare” is interesting. It’s such a coordinated response from Republicans that one would have to assume that it’s a thoroughly poll-tested idea. However, class warfare as it’s generally defined is a Marxist idea, and a positive rather than normative one. Class warfare wasn’t necessarily something that the workers should do, but rather is the natural state of relations between classes.
Of course, Marx generally viewed classes as not being rich-middle-poor, but labor-capital, and he might suggest a great example of class warfare was tax policies designed to benefit capital at the expense of labor. In fact, a dedicated 19th-century Marxist would view this policy as desirable, and in fact would be delighted at capitalists “heightening the contradictions” and further delegitimising capitalism with transparently class-based policies.*
*: The oddity of this position is one of the reasons these guys are no longer around.