Can someone explain how seeing this 'ISS' is somehow magically proving an RE? That would be like arguing seeing a plane overhead proves outer-space flight or something. You'll have to do better than that.
Sure. RE predicts when ISS will pass overhead, how long its transit will take, and the course that it will take for any observer at any location at any time. Please reference:
http://www.heavens-above.com/.
The RE argument is that there is no other technology available that will allow such short and accurately predicted transits expect orbiting spacecraft. Furthermore, even backyard telescopes can discern some larger details of ISS (general shape, whether a shuttle is docked). These images are consistent with predictions and not distorted by hanging lens.
I hope that helps. If I ever fail to answer a question you think I should have, please PM me to wake me up. Thanks.