Is it classy to drink red wine out of glasses meant for white wine?!

It's pretty irrelevant really. Unless you're planning to take so long drinking it that white wine gets too warm, the only other consideration is whether you need a narrow glass to keep your champagne fizzy...
And remember, if your guests/host are judging you on such petty nonsense, you really don't need to waste your time on them.

Classy? No, but it's not "unclassy" either. If you go to a tasting they'll typically use a neutral style glass that's more white-friendly than red in shape.

Other than champagne flutes (which are primarily visual) the wine glass is shaped to highlight the smell of the wine by either concentrating it (whites with a narrow top) or by allowing a lot of air to reach the wine (reds, very wide top). The stem is supposed to keep you from touching the bowl, so you don't transfer heat from your hand. Beyond that, some makers create very specific wine glass types with lip shapes and curvatures that in my opinion just get silly.

So drinking wine out of a wine glass in the first place, as opposed to a tumbler or plastic cup or whatever, improves your experience by allowing you to hold it and smell it and sip it with the best outcomes. Using the wrong "type" of glass isn't going to ruin the experience, using the right glass might make it a little better, though. So using a wine glass shows that you're at least trying to appreciate the wine. If you're drinking reds out of a champagne flute, you'll look a little odd, but I doubt anyone but wine snobs will care much.

It is better to use the correct glass. It's not a matter of style it's a matter of purpose. White wine is served cold and white wine glasses have a long stem to help prevent the heat of the hand from warming the wine. Red wine is served relatively warm and thus the problem of warming does not exist.

Those who speak of drinking from a bottle - be the drink beer, wine of spirits, are doing themselves a disfavour. Bottles are for storing drinks; glasses are for consuming them and there are special glasses for each kind of drink. A drink taken from a bottle will be far less satisfying than a drink taken from the correct glass for many reasons, including the inability to see the colour and sample the bouquet of the drink.

Glasses for red wine are usually wide at the neck to allow the wine to breathe and develop. White wine glasses are narrower but to my mind it does not really matter.

Bistro glasses can be used for both.

If you are giving a glamourous dinner party it might matter but most people are more interested in the company than the glasses.

Salut

Class has nothing to do with it in my opinion.

I am very picky about the glass used for anything I drink but not for the reasons you think. I guess I am just a creature of habit. I have a coffee cup that I'v used for 15 years and whenever I am away from home, my coffee seems to suffer in flavor because of its absence.

I'm the same way with wine. I could care less about red wine vs white wine glasses but I hate drinking wine out of plastic or god forbid styrofoam. I also hate those really thick walled glasses that are carved like waterford crystal that some low end restaurants give. Just give me a regular wine glass with a thin edge and a stem.

I don't think that classy or not classy is the issue here. You can drink your red wine out of any type glass you wish, even a dixie cup. Go ahead. Enjoy.

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I am a wino.

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I don`t think it really matters.
I think it only matters when you have fancy guests over for dinner.
but for everyday use it does not really matter

Why bother with glasses at all? Just pass the bottle around and slug directly out of it.

It does not bother me. People who obsess on class have little.

Does the wine come in a box? cause that shows true class!!!