Initial reactions aren't always accurate, people's views change, and 
science has its insurmountable way of convincing people. Gavin [1] 
and others [2] now cite selfish mining as a concern in the block size 
debate, and more importantly, the paper has been peer-reviewed, 
cited, and even built-upon [3].

Let's elevate the discussion, shall we?

[1] Here's Gavin concerned about selfish mining: 
http://gavinandresen.ninja/are-bigger-blocks-better-for-bigger-miners

[2] Here's Adam: 
http://bitcoin-development.narkive.com/mvI8Wpjp/dynamic-limit-to-the-block-size-bip-draft-discussion

[3] This is a very nice extension of our work:
Ayelet Sapirshtein, Yonatan Sompolinsky, Aviv Zohar:
http://arxiv.org/abs/1507.06183