It's a dispute I've seen several times. I like it because, it *sounds* cool, and there's *nothing else alive that might count as a dinosaur* to point to in disproving it.
Some scientists argue that birds count as reptiles, which I find more egregious just because we have living reptiles with large enough physical differences to make merging the two kind of pointless.
If anything, the word "dinosaur" is outdated and animals within the class should be partitioned between reptiles and birds. but until then i'm happy to treat the birds as carrying on this torch we once thought completely extinguished. They're absolutely insane creatures in their own right and more then deserve that honor anyways!