Allegedly, on or about 02 January 2014, Ales Kozumplik sent:
In practice however, a user doesn't type 'dnf erase -y kernel' by accident and we don't feel the need to protect users who really know what they are doing from doing so. It's the same situation as 'rm -rf /boot' or 'rpm -e --allmatches kernel'.
I tend to agree, though it's a hazardous possibility, and the sort of thing that's usually covered by an alias, or required option, to the command.
While I might well install/upgrade a non-specific kernel. If I were going to remove a kernel, I'd be specifying which particular one. And those doing something just like "yum update", with no further parameters (perhaps, other than the less-than-clever "-y"), the installing of the latest kernel and removal of the oldest one, ought to be automatically handled the way it always has done (by the update routine).