Imagine a heated discussion between two people. Let's say they are debating whether or not eggs are bad for you. The discussion has been going on for a while until one person says something along the lines of "Well, obviously, eggs are bad for you because..."
The word "obvious" seems harmless and, to my knowledge, is used fairly commonly in today's language. It's a simple word, but it's a heavy one and implies a lot. Whether or not you may mean to, using the word "obvious" implies the other person or people are missing something. It implies they are an idiot.
When I scientist comes up with a hypothesis, they have to test it. If that test confirms their hypothesis, that doesn't automatically mean they are correct. If they're test confirms they're hypothesis, it then has to tested by other scientists and confirmed by them. Now, the scientist who originally came up with the hypothesis may think "it's obvious I'm right because my test worked!" But that would be wrong. Because it's not obvious. It may be "obvious" to that person in their circumstance, but that doesn't mean it will be "obvious" to anyone else.
There's nothing wrong in thinking what you believe is correct and it's not wrong to think someone else's belief is incorrect. What is wrong is how you present that belief. If you present it in such a way that it's "obvious you are correct" and put down anyone who believes or thinks otherwise, then that's the wrong way to go about it. At that point, you are arguing for your own ego. Profitable arguing should be about finding the truth, not stroking one's own ego.
This is why I think the word "obvious" is dangerous. In nearly every case I can think of, it puts down. The implication is the other person is missing something that they should be smart enough to see. Plus, it's not necessary. You can confidently present your facts without using this word and it doesn't change anything.
To end, I will say I don't think everyone should avoid using the word "obvious" at all costs, lest we offend anyone or make someone feel bad. That's not my goal or my intent. My intent is to get you to think and realize words have meaning. This can be hard in a day when we use "literally" wrong, but words literally do mean something. They are our way of communication and the words we choose reveal something about ourselves. It is important to pick the words we use carefully and always seek to talk TO someone, not DOWN to them.