I used to ascribe to the dictum: "The best counter to bad ideas is good ideas".
This was based on an (unwarranted) assumption that people are open minded and rational enough to look at the options, weigh them against each other and then come to a considered opinion. Unfortunately, for a large (and apparently increasing) section of the population, this is not the case. Case in point - believers in trickle down economics, Objectivism and economic nationalism.
So, then I moved onto the dictum: "Bad ideas exist to be destroyed"
This was based on an (unwarranted) assumption that if you showed people why the ideas they believed in were bad, and hammered this point into them enough, they'd jettison their bad ideas. Unfortunately, when shown that their ideas are bad, there is a strong psychological drive to double down on the same idea because of the evidence against it. See also, flat earthers, creationists, Scientologists, and anti-vaxxers.
Now I (reluctantly) believe that some ideas are inherently harmful, and like a fire should be denied oxygen to prevent spreading.
This is because the way we consume information has become a series of self-selected and algorithmically-generated silos. People are no longer seeing opposing view points, unless its someone on their 'side' (whatever that may be) dismantling/debunking/ridiculing someone on the other 'side (whatever that may be).
In this new world, people are no longer exposed to good ideas to counter the bad ones. People are no longer exposed to rigorous critiques of whatever heinous notion they ascribe to. Instead, they are able to consume a diet of content that is tailored right into their comfort zone - opposing voices are drowned out (except when one of the pack becomes weak/sick/feeble enough to warrant a pack feeding frenzy) and biases are met by voices increasingly in lockstep.
And yes, the reason that I'm on this website is so that I hear voices that are in opposition to my own ideas (and no, that wasn't the reason that I originally came here).