Rorschach is a fascist, he only works in absolutes and while the Batman tries not to kill, Rorschach has no such regard for human life. He detests the junky as much as the murderer, for him there is only pureness and evil, every little bit of amoral behavior will be punished and at the same time he considers his own vigilantism as above the law.
He's a misogynist who thinks that the Comedian raping Silk Spectre was just a "moral lapse". He holds even for his time outdated socially conservative views and strongly opposes what we would call (gender and sexual) minority rights.
Rorschach is unbending and uncompromising, he is beholden only to his conservative rigid views of black and white morality with no room for shades of grey. That might not sound so bad at first, but if you think about it, that is definitely not someone who you want as a judge of people.
On top of that he's a far-right believer, he's not a government man in the same way the alt-right are not. His thinking is deeply conspiratorial and paranoid with a huge dollop of delusion. He's better described as an Ayn Rand paleolibertarian.
Thinking about it he definitely would fit right in with today's alt-right with the only difference that (if - and only if - he would not buy into their conspiracy theories - and he's very much likely to do so) he would detest Trump for his lying.
But Rorschach is definitely the kinda guy who'd shoot up a pizza place looking for tortured kids in the basement.
I love him as a character, he's one of the best written vigilante "heros" out there but what's so fascinating - to me at least - is that his principled moral conviction is contrasted by how immensely unlikeable this man is and how his moral uprightness relies on the moral compass of a deranged 11 year old with a gun.
When I was a kid watching Watchmen, I thought Rorschach was badass with his fight scenes and detective work, like breaking into Dr. Manhattan's compound. His fight scenes with the swat guys was badass.
Then they make a point to show you multiple times throughout the movie, this gross, shabby looking dude carrying around a "the end is near" sign, following people and giving them the creeps. They definitely didn't go into the comic enough though.
Rorschach is Batman but worse in every single way. All the childhood trauma and mental illness without any of the money, good manners, or training, and with several extra doses of far right conspiranoia and misogyny.
If you read Rorschach as the good guy in Watchmen, you completely misinterpreted what Moore was trying to say. If there's any good guys in Watchmen (or at least not bad guys), and that's a big if, it's the folks around the newsstand, obviously not counting Kovacs.