Just because you don't believe something is related to something doesn't mean it isn't. If Bernie supporters start using the hammer and sickle and say they don't associate it with communist Russia, are you telling me that means the symbol isn't related?
As for tarnishing their achievements, couldn't we say the same about every bad actor historically? The first thing the US did when it got to Iraq was take down all the Saddam statues. Should we have kept those up because they were popular with a large group of Iraqis and because he had accomplished a lot? The first thing we did when we setup West Germany was take down all the Nazi statues, should we have kept those up because we didn't want to tarnish the achievements of Soldiers who happened to join a bad cause?
The problem is the ONLY time you want to use this logic about keeping up statues of a bad actor is in regards to the confederacy.
The other reason they should be taken down is best expressed by Robert E. Lee himself, who was against the idea of glorifying or building statues to Confederate troops:
https://www.pbs.org/newshour/nation/...rate-monuments
“I think it wiser, not to keep open the sores of war but to follow the examples of those nations who endeavored to obliterate the marks of civil strife, to commit to oblivion the feelings engendered.”
So if you actually want to honor Robert E. Lee, perhaps you should do what he says.