I recommend checking out some of the Taiwan blog coverage on this, including my own That's Impossible, The View from Taiwan, and Fili's World.

Video here:
http://news.bbc.co.uk/2/hi/asia-pacific/7681711.stm

great footage of attack on youtube here: http://jp.youtube.com/watch?v=wuozDzofIhw

1st, Zhang Mingqing works at "The Association for Relations Across the Taiwan Straits,ARATS" ,the affiliated "non-government"body under the State Council Taiwan Affairs Office,while the Strait Exchange Fundation in Taiwan is the correspondence body in the cross-strait civil affair talks.
2nd, He is the vice-president of the association,and does not openly carry an "envoy" role -Chen Yunlin,the president of ARATS,is going to visit Taiwan as an envoy in the very near future, so Zhang is probably paving the way there.

Chen Yunlin's Taiwan visit will be postponed, since he's under intensive training in a Shaolin temple somewhere in the mountainous area of the Middle Kingdom. It is said the "divine tree" of Tainan temple has more lessons to give this time. Ouch!

TW's Democratic Progress Party(aka Green party) is on edge of turning into a NAZI party. From this video you can clearly see the racial hatred is real. Attacking on a nearly 70 yr old scholar just because he is Chinese and has a role in Chinese government??? What i've read from the Internet is that, as a scholar from China's Xiamen University, this guy was invited by a Taiwanese college for a conference. In order to make the trip less political, he even skipped the capital of Taipei and stayed only in the city where the college is located.
Well I guess fighting is just part of TW’s political culture. Watch these videos:
http://www.youtube.com/watch?v=Jo-TajmBr1s&feature=related
and here:
http://www.youtube.com/watch?v=a_-Eigd7RbU
and here
http://www.youtube.com/watch?v=ht9WEpdi5JY

Danwei:

It's not clear whether Zhang was pushed or fell. Videos unfortunately do not have good angles on the incident. A man did leap on his car but there's a long history here of the Dark Side using gangsters to disrupt and discredit activism so I'd be skeptical of which side he was on. You can see the incident on my blog where I have links to many videos.

Why he was accosted is obvious: he's the number 2 man in ARATS with a long history of making violent threats against Taiwanese lives, and Tainan is a hotbed of Taiwanese nationalism. If you threaten people with violence, you can hardly blame them if they react strongly. IMHO they showed remarkable restraint, all things considered.

It should also be noted that emotive grandstanding is a way politicians get noticed here. There was nothing out of the ordinary about Wang's behavior either.

It would have been far stranger if Zhang had gotten out of Tainan without a protest.

Nothing happened that was out of the ordinary for a taiwanese protest, where pushing and shoving are pretty common. It was just the first time they were directed at The Man from Beijing instead of The Man from Taipei. Also, his police escort had vanished, meaning that all that pushing and shoving and motion, instead of being dissipated against a police line, actually reached its symbolic target (oops!).

Zhang was protested all the way back to the airport. As someone whose children's lives Zhang and his bosses have repeatedly threatened, I say good riddance.

Michael

Update:

The guy who jumped on his car is a locally known independence activist with a two decade history of uh...energetic activism. :)