> it is fundamentalist if the only reason for the rejection is that it's proprietary

Personally I don't use software that I cannot review myself for tasks that are important to me. That includes reading email. Hence, the reason for rejection is that it's not open source. I don't see how this makes me a horrible fundamentalist, but maybe you care to enlighten me :)

> it's harmful for the entire ecosystem

I also completely fail to see how me personally want to review source code is harmful to the "entire ecosystem" (I assume you refer to the FOSS ecosystem?)