Bad history is a big problem in the pagan community (which is not to say it's limited to the pagan community, unfortunately it's not). It's everywhere, and sometimes it can be really hard to get down to the historical facts of particular topics - even for avid history lovers.
Why does it even matter? Why should we care about historical facts? Simple - these are our roots! Through studying history we can see where many aspects of our lives originated - the meanings behind many beliefs and traditions. We can see how cultures, religions, even the languages we speak evolved over time. When we see this, it's clear how our history is our foundation - how we continue to build on the past... and how the future will build on what we do today. History links us to our ancestors, and it will link our descendants back to us.
I sometimes see pagans saying they don't care how X deity was worshiped in the past, or similar statements. Look, I'd never tell someone they have to do everything exactly the way it was done in the past, but ignoring hundreds or thousands of years of knowledge? Why in the world would you shoot yourself in the foot like that? Even non-reconstructionists can benefit from the knowledge these people worked for. Obviously those ancient devotees had a different cultural filter, not everything they did or believed will benefit every person today, but how can you know unless you look?
New religions, new traditions, new beliefs and ideas are not bad. Something does not have to be old to be valid, to have worth - yet sometimes false histories are attached to new ideas for exactly that reason. This isn't necessary. If an idea is good, if it works, if it benefits people, then it should be able to stand on its own. Saying something is not historical does not mean it has no value.
These are just a few of the reasons that good history matters. Heck, if for no other reason, doing a little fact checking can prevent you from looking ignorant. That's always nice, right? Of course, as I said, bad history is everywhere. Sometimes it can be hard to miss, and you pick up a few bad facts along the way. It happens to most people at some point - I know I've fallen into a few bad history traps. Or, sometimes we think a source is trustworthy - that they've done their research - when that may not always be the case. Bad history can be hard to avoid, but there are some history myths out there that are so easy to disprove, yet still get passed around as fact. I know historical research doesn't always seem fun or spiritual, but sometimes it needs to be done... and frankly, we absolutely can benefit from the wisdom of our ancestors, if we bother to listen.