Why should it have an effect? they are 2 separate currencies,and i don't think etherium is that popular..
I think they are talking about the recent issue of DAO. The hacker didn't even sold even a single ETH, they locked up the child DAO which the hacker transferred it to.
True, He didn´t sold but investors lost confidence and they sold, It was on levels $20 and after crash $12.
While than the BTC value remained the same on this event.