This script will remove all lines that start with # along with all comments.
Whatever file you choose I suggest you view first then execute
sed "/^\s*#/d;s/\s*#[^\"']*$//" /etc/dnsmasq.conf && sed '/^\s*$/d' /etc/dnsmasq.conf
sudo sed -i "/^\s*#/d;s/\s*#[^\"']*$//" /etc/dnsmasq.conf && sudo sed -i '/^\s*$/d' /etc/dnsmasq.conf
All information on this site is shared with the intention to help. Before any source code or program is ran on a production (non-development) system it is suggested you test it and fully understand what it is doing not just what it appears it is doing. I accept no responsibility for any damage you may do with this code.