Daghoi,
These things go on all over Beijing, and other cities and towns too. There mostly frustrated parents of Children that haven't shown any interest in finding girlfriends and boyfriends of there own. And yes you've guessed it, some of those children are gay, but the parents are unaware of that fact...haha!!
These parents will go to all the gathering places in there city or town, and if they are still unsuccessful, will even travel outside of there city too.... It's not unusual to see them showing Degree certs, photo's of houses/apartments, even monthly bank accounts slips. How successful these match making things are is any-one's guess!! They can get into quite heated discussions, but then that's second nature to them, raising there voices doesn't normally mean anger, you need to look at the faces and mannerisms to see if there is anger or not!! ...haha!!
Just another little one, of the Chinese custom shocks that you will come across on your trips to China, not that you would know what the hell was going on, unless like yourself you had someone to point it out and tell you what was going on... lol!!