It can't be helped that they are idiots, and want to believe proven liars like Ward Churchill.
And for the latter part, that is wrong. Most of the Indians died off in the very early 1500s, and were dead most of a century before the first Settlers even arrived in North America. And most did not die of smallpox, they died of the common cold, the flu, measles, and chickenpox. By the time smallpox reached them in the 18th century, the survivors of those first pandemics had resistances pretty comparable to the Europeans and died in roughly the same numbers.
The North American Smallpox Epidemic of 1775-1782 killed over 130,000 Americans of European descent before it finally burned out. And ironically, traders from the Hudson Bay Company kicked off another epidemic in 1782 that did affect the West Coast, with mortality rates comparable to those that were seen among Europeans on the East Coast almost a decade earlier. That is the amazing thing about smallpox, nobody has "immunity" to that one, that is why it was such a scourge for tens of thousands of years and decimated people anywhere it arrived. Be it 1800s England and France, or 1900s Boston.
And that's alright, they gave back just as well. The Europeans gave them the cold and measles, the Indians gave them back syphilis.