It isn't about throwing mud, it is about winning elections.
This idea that the Democrats should throw mud at Republicans misses the mark.
The Republicans are "throwing mud" in a very strategic way. They understand that White middle-class suburbia is where the battle is being fought... and they are telling a narrative that these people (whose votes they want) are under threat from the Democrats.
Maxine Waters is helping the Republicans... her mud is telling White middle-class suburbia that they are under threat from Democrats. Of course, this isn't her intent... she is speaking to her base. Her base is not where the battle is being fought. Her mud throwing is strategically stupid.
If you want to win elections, you have to accept the reality of the battlefield and design a intelligent strategy. You need to accept that reality isn't equal and reality isn't fair. Your opposition has advantages, and you have advantages. You want to use your advantages and minimize the impact of your opponent has where it counts.
For God's sake, Democrats! As good as it feels to throw mud... alienating the very people you need to win elections is an incredibly stupid political strategy.