Example themes often repeated that might look strange to outsides (and as well as many insiders)...
Conspiracy theory at every level
Unrealistic Hot Button issues like terrorism (within an hour of falling to earth, people were posting theories on the shuttle being brought down by terrorists)
Government is evil.
Laws are evil except those that we like.
Cops are jack-booted power hungry thugs who love nothing better than harassing gun folks and the opportunity to shoot people.
Quick to support other gun owners simply because they are gun owners who were involved in shootings, legal fights, etc. without first knowing the issues and then sometimes afterwards as well.
Posts on intent to commit murder of LEOs who might have to act on laws pertaining to gun confiscation.
Admissions on knowingly breaking the law by carrying concealed in places where carry is illegal because the gun owners don't like the law, think it is wrong, or simply that it does not pertain to them. So much for gun folks being "law-abiding" and doing nothing wrong.
Posts on bizarre gun-related behaviors such as wearing 24/7.
Disallowance of concealed carry means taking away one's right to self defense. Of course this is incorrect, but that is often the sentiment expressed. Disallowance of concealed carry does not mean you can't defend yourself, only that you are not allowed to have a gun to do it.
I am sure I have forgotten many others, but many of these sound strange to non-gun people, even frightening.