A lot of the advice in this thread is absolutely appalingly terrible knee-jerk *******s.
Once you get past a certain age, little 'bullying' is intentionally malicious. Its far more likely that it is just insensitive people who have not come across aspergers before 'having a laugh'. These kinds of people can easily be reasoned with, or shamed, into acting more reasonably. The very worst thing he could do is threaten them or otherwise escalate things (he would permenantly become "that psycho").
1) Encourage your brother to rise above it. The facebook stuff is easily avoided by privacy settings he should have set already.
2) With regards to specific issues like noise, get him to speak REASONABLY to the culprits - no blame, no accusations or threats or other escalation, just say that its waking him up at night, and do they mind trying to avoid that. Even if they are doing it on purpose, this sets a record of reasonable behaviour which will later be extremely useful if, for example, the dean or whoever needs to be involved. In most cases they will make more effort.
Note that in many halls, coming home while drunk makes a certain level of noise inevitable - its one of the quirks of halls life. If it is genuinely unintentional and continues, he just has to get over it, get earplugs or find other ways to cope. At my first year halls there were a couple of noise nazis who used to get extremely angry at evening and night time noise (in a very old building with poor insulation, even normal conversation carries). Tbh, so long as the noise was not unreasonable it was their problem - having a quiet conversation in the kitchen before midnight is completely reasonable and if they are so on edge they cant sleep, that's definitely something for them to work on.
3) If it genuinely is malicious (not just in your brothers view but objectively speaking), then consider shaming them directly - send them a plea by message on facebook, saying they are making him miserable. This is a last resort as you should not be fighting your brother's battles.
In some cases the 'bullies' feel justified in their behaviour because of eccentric or anti-social behaviour on the part of the 'bullied' - in this case the easiest way out is to identify the eccentric or anti-social behaviour and STOP DOING IT. For example, in my halls there was a guy who EVERYONE was hostile to because he used to play extremely loud metal music through an amp late at night (and believe it or not, sometimes plug a mic in and kareoke along to "BULLET IN MY HEAD BULLET IN MY HEAD!". I lived next to him and it would wake me up (I'm a deep sleeper) 3 nights a week or more, usually around 3am though sometimes later. I (and several others) tried to reason with him on several occasions, but he just ignored us (literally, no verbal response). I'm sure the hostility everyone projected towards him for the rest of the year could be called "bullying" (for example, he would never be invited to halls parties or group meals), but really I have no guilt about it, he was horribly and unrepentantly antisocial and caused me a lot of suffering. Even if he had some kind of disability (as I guess is likely), this shouldn't mean I should have had to put up with his behaviour.