What does 上纲上线 mean? I only know about 上网 or 上线, that is, to go online the Internet.
But 上纲上线 can be heard from time to time, but the speakers often cannot clearly define the meaning. Neither can I.
上纲上线 means raise common things (actions, opinions) at the level of big issues about nation, society, morals or politics.

A: 好啊, 你喜欢外国货是吗? 你怎么不买国货? 叛徒!

(A: Wow. You like foreign products? Why didn't you buy products made in our country? TRAITOR!)

B: 别上纲上线, 完全没道理.

(B:stop, that's nonsense.)

A: 我觉得不一定非要让座, 我也很累啊.

B: 你真没素质.

A: 你总是喜欢上纲上线, 让不让座跟素质有什么关系?