I dont think its fair to berate the office staff or try to push through the doors when the staff enforce the rules. I agree it wasnt a very nice experience for the OP but a small bit of common sense would have prevented the entire debacle.
Yep. OP was trying to break a rule and wasn't let. Too bad !
SW offices have signs at the door stating specifically that there will be no re admittance to the building if you leave 10 mins before the official closing time. Obviously this extends to trying to get back in after they have closed. This fact is also printed on the tickets that you take to get to see someone. If OP chose to ignore that information, too bad.
I have seen SW staff being verbally and physically abused in SW offices by the people that they are trying to assist. The security staff hired to protect the staff and the building are probably people who take no guff and stand their ground. They have to be. If you choose to confront them and don't like the consequences, again too bad. If security went too far during the altercation, it will be captured on the CCTV cameras that are mounted in all SW office doorways. Call the Gardai and have them deal with it.