"Guarantee" is just an expression. I can tell you if my brandy is at room temperature my fingers are not going to warm it up before I drink it.
Maybe a snob or a connoisseur will think the glass will make the difference but I still say it is a mind game of expectations and I am not saying that the proper glass doesn't make that difference as it does to me. I do prefer drinking out of the proper traditional glass but a Martini is still going to taste the same no matter what the shape of the glass.
Wine glasses are just more tradition. Since reds are generally served room temperature and whites are generally served chilled the reds can be more forgiving in surface area than whites but a red could still be served in a narrow vessel. The only thing that bugs me with wine glasses are people who hold them by the vessel and not the stem, but then it really only bothers me when clinking for a toast and not getting the ring because they didn't hold by the stem.
Talking glass to glass here, not polyfoam to paper or even to ceramic for coffee. I can agree changing the material will change the taste. But my Guinness Stout will taste the same whether it is in a small sampling glass or a pint glass, but my experience will be at its height in a proper pint glass, and I can't imagine ever enjoying a Guinness and drinking it out of a can.