First off, you are indeed entitled to believe whatever you want, but that does not change the fact if your beliefs are justified or not. If you have no evidence that the universe is in fact created, then you have no justification for assuming a creator.
Secondly, what on earth does this have to do with Karl Marx?
Consider this, justifying and evidence are two different things.
jus·ti·fied
ˈjəstəˌfīd/
adjective
adjective:
justified
1.
having, done for, or marked by a good or legitimate reason.
Simply put, justifying a belief on someone is simply convincing them to also believe in it. Let's be objective on this, and not convince this argument to its end. Now this aside, when we're talking about God, things can get messy. God has no evidence, and cannot simply have evidence because God can be anything, really. We're talking about an entity that is claimed to have powers outside time and space. Who knows, maybe he's a unicorn too. However, using the Bible or any other form of "justifying" to prove if God exists is a weak argument, and arguing if the Bible is morally wrong or right is not a strong and solid way of proving if God exists. So let's not justify.
If you have no evidence that the universe is in fact created, then you have no justification for assuming a creator.
The universe is created, we live in it. Of course, unless you consider that our 5 senses and our mind is tricking itself into believing what we're living in is actually real and we're in some kind of matrix, then I get your point.
So, on the realist side, the universe is created. There is a creator, we just don't know if this creator is this God we're all talking about, some massive supernova (or whatever), or perhaps something more.
Secondly, what on earth does this have to do with Karl Marx?
Karl Marx is part of this argument because he Karl was created in the universe, and we're talking about the universe.