Shadowpurser - Step one would be to try and talk to this chap, 1 on 1, explain how you and the others you have discussed it with feel and quite simply, "What is wrong?" Be sure to have your facts and details ready as he may ask, "and when was all this supposed to have happened?" etc. etc.
If you know certain F/O's well enough you could get them to do a bit of detective work as well, try and find out why he chooses to be so rude and difficult.
After Step One, if it doesn't work, you will have to consider what other proper grievance procedures are open to you within your company. Strongly suggest that if it gets to this stage you have by now become a group! Each member should have their own version of separate events so that it can be seen that this is a widespread and ongoing situation.
Finally, as I remember from my days as a F/O, being the only other crew member to turn up for the captain's room party, listening to a very sad tale of how he had been seriously dobbed in to management by some cabin crew previously over some incident or misdemeanour, details got to his wife and he finished up divorced, broke and demoted!!! Thereafter he found it hard to be nice to CC. NOT the way to handle such a situation but I just mention it in case it has some relevance to your case.
Best of luck, do your groundwork
very thoroughly and make sure you have all your facts and details absoloutely correct.
