Rorschach is isolated from society by 3 things, his thoughts, actions and ideas.
Rorschach's actions put him as a sociopath, unable to let go of any thought that evil should be punished permanently by death. The things that Rorschach does isolate him from society.
Rorschach's thoughts and ideas have him characterized as a Nazi and paranoid weirdo. Anything new in the city that happened put him on edge and very volatile.
However Rorschach's unbound paranoia and deep-seated suspicion as well as his devoid compassion to criminals make him a excellent vigilante, as well as come in handy when extraction information from hardened criminals and seedy drunkards.
On the other hand these characteristics that make him a great adversary on dark nights and seedy bars separate him from society even further for people fear what they cannot understand such as Rorschach's mind which we all know is as twisted as an Oriel nest.
Rorschach's isolation from society make him a lonely character, and one of the for feared and respected for his uncompromising attitude in his goal to stop any and all evil from patrolling in his city and onhisstreets. Rorschach's unrelenting attitude and empty compassion of human nature push him away from people.