Let me elaborate with some examples that should drive the point home. The Globe is warming, this is something that is not denied by any climate scientists. Yet there are still people that express opinions that the global climate is not getting warmer. Now if someone believes that the globe is not getting warmer, you cannot have the deeper conversation that the increase in temperature is anthropogenic. So the bad idea in the beginning is the false idea that the climate is not getting warmer, and these debunked lies still get mentioned by climate change deniers around the world as they believe the dangerous minds that spout them. If you have 45 minutes this video embedded here gives a few perfect examples of this type of denial in action. It also gives you a very good idea why we have to combat bad ideas.
Then look at the highly dangerous myth that the MMR vaccine causes autism. This whole junk science story started in 1998 with the publication of a fraudulent paper in the Lancet journal. Now it is 2016, and this fraud is still believed by many people. This is a bad idea propagated through society that can, simply put, lead to dead children and babies. There is no excuse for believing this autism link, but some people are not exposed to the truth and so theycontinue believing. Is this a good enough reason to continue exposing bad ideas?
Now I will say if you cannot accept the above truths then you are either a climate change denier or an anti-vaxxer or both. Personally I think the label moron fits, but that is just me.
So what about religion? Is this a bad idea? The answer for me is a simple yes, so allow me some time to elaborate why. We as people are affected psychologically and physically by everyday situations. In fact some of these situations can harm more than others, for example the death of a loved one can cause a great deal of psychological stress. So how do you think a person would feel when they believe that the loved one that died is enduring an eternal torment in hell. Naturally most believers don't want to think about this all the time, but sometimes they will. Recurring trauma, somehow I think this is a bad idea that should be combated. Lastly, if the fact that your friend burning in hell does not bother you, then you are a psychotic prick.
Now these are just three examples of bad ideas that can cause harm to you personally or to society at large. The problem is that these examples are just the tip of the iceberg, and we have dangerous minds out there selling this bullshit. This is why I probably will keep writing for a long time and keep hammering at the same subjects. Who knows maybe someday somewhere someone will read this and it could end up saving a child's life.