This has nothing to do with arrogance. There's a simple reason: The majority of the people here don't understand german so english is agreed on upon using this forum. This has especially two benefits:
1.) If you have problems and you describe your problem in english than a lot more people actually understand it and might be able to help you. So you benefit directly from using english here.
2.) Other people may have the same problem as you. If you write it in english and someone has a solution for it then those people will be also helped quicker since there is already a solution that they understand and can apply.
However if you think Falko's attitude as being arrogant, well there's nothing I can do about but we both know it's not true. You should just have a look how often Falko has given here support to others...