It's not my responsibility to deal with messages the senders aren't
serious about being read.
It's up to you of course but if that's your opinion then you always
have the option of simply not reading messages that are sent (against
list guidelines) with HTML parts that suggest using fonts that are too
small for you.
I know what to do to read messages with tiny fonts -- if I can see enough of it to decide they're interesting.
So far, only one correspondent, whom I have by-and-large concluded doesn't have anything interesting to way.
What I'm offering to those who send messages that they seriously consider to be worth reading: You ought to make them readable. If you make it hard for recipients to read them, they'll ignore your wisdom.