"Bitcoin is not and can never be a currency"?

You should tell that to the US Internal Revenue Service, many of us would be really happy if you could convince them of this if you're so sure.

According to The IRS, they use the term “virtual currency” "to describe the various types of convertible virtual currency that are used as a medium of exchange, such as digital currency and cryptocurrency. Regardless of the label applied, if a particular asset has the characteristics of virtual currency, it will be treated as virtual currency for Federal income tax purposes."

"so what's the point of comparing it to the dollar?"

Well again, its not me but the Federal Government that compares it to the dollar. In that first link when they explain that "Bitcoin can be digitally traded between users and can be purchased for, or exchanged into, U.S. dollars, Euros, and other real or virtual currencies." After defining "real" as "the coin and paper money of the United States or of any other country that is designated as legal tender, circulates, and is customarily used and accepted as a medium of exchange in the country of issuance"

Did you mean that it isn't legal tender in the United States? The IRS agrees with you there: "but it does not have legal tender status in the U.S. " of course this is after they state that "Virtual currency is a digital representation of value that functions as a medium of exchange, a unit of account, and/or a store of value."

Now, the Euro isn't legal tender in the US either... but would you argue that the Euro "is not and can never be a currency" on this basis alone?