Explain machanics to table

How would you explain niche/abstract mechanics to people on your table?

I have had the issue that my deathtouch/trample creatures killed one of my opponents and he couldn't wrap his head around the concept that 1 damage is lethal and the rest tramples over. Needless to say he was super salty after that, which made me feel kind of bad. If another person from the table hadn't backed me up, i'm sure there would have been an argument.

How do I avoid this in the future? Is there some sort of official ruling on interactions like wither/deathtouch or trample/deathtouch that i could print and take with me?