The first time that I saw someone holding their wine glass by the base I assumed they were a real wine snob. Now, maybe they were a wine snob, but there actually is a good reason for holding a wine glass by the base.
Wine etiquette usually dictates that you should always hold your glass of wine by the stem and not by the bowl. This keeps your hands off the bowl and avoids smudges and marks that could otherwise detract from the appearance of the glass.
But, if you happen to own very fine wine glasses or get served from a very fine wine glass you’ll find that the stem can actually be quite narrow and even potentially brittle. It’s in this situation that holding your wine glass by the base, or foot, is recommended. You’d really hate to be holding an ultra-high-end glass by the stem and find that the small amount of pressure you put on it causes it to snaps. Embarrassing, costly and potentially hazardous to your hand!
So, holding a wine glass by the stem is usually the proper thing to do. But holding an extremely delicate wine glass by the base is actually the practical thing to do. Cheers!