They have (had?) a requirement to block certain sites (e.g., CP), and their CEOs could be sent to jail if they didn't. So from their perspective, Mozilla was not doing a good thing as it was causing them grief in being able to follow the law:
> for their proposed approach to introduce DNS-over-HTTPS in such a way as to bypass UK filtering obligations and parental controls, undermining internet safety standards in the UK
* https://www.theregister.co.uk/2019/07/06/mozilla_ukisp_valla...
They have (had?) a requirement to block certain sites (e.g., CP), and their CEOs could be sent to jail if they didn't. So from their perspective, Mozilla was not doing a good thing as it was causing them grief in being able to follow the law:
> for their proposed approach to introduce DNS-over-HTTPS in such a way as to bypass UK filtering obligations and parental controls, undermining internet safety standards in the UK
* https://www.ispa.org.uk/ispa-announces-finalists-for-2019-in...
So yeah, I can understand why they'd be salty. As someone who works in IT I'm also salty at DoH for similar netsec reasons. (DoT is another matter.)