Stealing IP without contributing to creation costs is bad behavior on several levels.
There is a difference between "I can do this bad thing, because you have already done it" and "this thing is not bad, otherwise you wouldn't have done it". Tu quoque addresses the former situation, not the latter.
And no, tu quoque definitively intends to discredit the opponent's argument by asserting the opponent's failure to act consistently in accordance with its conclusion.
This applies to whataboutism, and exactly what we're talking about in this thread of deflecting back to the U.S.'s inconsistent behavior in the past.
Using the argument that some country did the same thing 100 or 200 years before is a child's argument and holds no weight. The Chinese government by taking advantage of the international order developed by the US has sown the seeds for the trade retaliation that is taking place today (to the detriment of everyone).