There are a number of bad precedents being set over the last two years. Start with Trump refusal to obey subpoenas as well as blocking testimony.
I can't blame the Dems for wanting to fight fire with fire. Besides, Kavenaugh was NOT properly vetted and the nomination was rushed through.
As I've stated before, the GOP died with Bush43 and Trump is a result of that death.
Politics will get a lot uglier and may never return to normal. If you look at how the USA is trending, the Dems are more likely to get a super majority in the not to distant future. And, like any good pachyderm, they won't forget.