Ignoring the statement, "I have been following SS for one year" and addressing the main concern about your family and their idiotic views on milk....
So look, you can choose to argue with people who have no knowledge within the field they're discussing or you can choose to ignore them and make it a fun game. Basically, if you try to counter them with evidence and explanations you're trying to make them understand science in a logical manner where they have already demonstrated the inability to do so.
If it were me, I would respond antagonistically- asking how in the f*ck are they coming up with these conclusions? Where is the data (not histrionic editorial pieces) and why do they feel so strongly about the topic in the first place? After I got tired of that, I'd probably just lie to them and tell them I stopped drinking milk- or send them memes of cows.
Honestly, I don't get why people care so much.
Also, for reference the data overwhelmingly suggests that milk is health promoting and associated with improved health metrics without any indication it is cancer, obesity, or other disease promoting.