Physical violence or the threat of physical violence is hardly the solution though is it? You're right to be clear about what you might not be willing to do especially at short notice but nearly getting into a fist fight over it is a bit dramatic and is hardly likely to help your cause in the long run. They say that diplomacy is the only true art form. Perhaps something worth remembering next time you're in a similar situation in any country.

Now these 'English corners' seem to be something of a bugbear for many FTs. My definition of an English corner is that it is a student organized and student lead event that is open to anyone to attend and talk freely about any subject they wish. The ideal place for it to happen is outside on a busy corner of the campus where passers by may drop in and out as they wish. If your school is telling you (the teacher) to prepare for and organize English corners then you are probably being stitched up into teaching what is more like an extra oral english class. My advice would be to take a pro-active approach to the situation and offer to help the students get the ball rolling on setting up an English corner that takes place at a specific location at a specific time every week.

This is certainly how English corners operate at my uni. I attend about 50% of them for anywhere between 10mins and 2hours. This was at the request of students and I was happy to obilge them on the understanding that this was still 'their thing' and that I'm going along to support their efforts. The events themselves are well attended and sometimes there are some heated debates on genuinely interesting topics. They are very useful for the students oral English. It's interesting how rarely the interests of students get mentioned on this 'teachers' board.