You mean like this evidence?
Cometary Asteroids
There are ALOT of things wrong with that page, too many to make an exhausive list. But at a glance:
Comets are often called “dirty snowballs” by astronomers.
No, they're called "dirty snowballs" by
journalists, usually because they don't know any better. Astronomers let them go on calling them that because they know the journalists don't know any better.
Comet Tempel 1 resembled an asteroid more than a chunk of muddy slush. Craters, boulders, and cliffs were observed—nothing like a snowball venting. Water vapor was discovered near the comet, but there was too little ice on the surface to account for it.
Which, if scientists had expected to see any evidence of
surface ice or active venting, would mean something.
Shoemaker-Levy 9 exploded when it encountered Jupiter’s magnetosphere,
No, it exploded in the upper atmosphere. Jupiter's magnetosphere is millions of kilometers in diameter and SL-9 passed through it twice before finally crashing into the planet.
Comets travel through a differential electric potential as they move toward the Sun. The variable electric fields cause visible glow discharges. Rather than “dirty snowballs” or even “snowy dirtballs,” comets are electrically active, solid bodies.
... said no data, ever.
So hot that extreme ultraviolet light and X-rays were detected radiating from
comet Hyakutake.
No they weren't. And the page this links to demonstrates a very poor understanding of how X-ray telescopes work or how they are used.
“The flaw in the conventional approach is that only gas-phase chemical reactions and reactions induced by solar radiation (photolysis) are considered. The far more energetic molecular and atomic reactions due to plasma discharge sputtering of an electrically charged comet nucleus are not even contemplated…The hydroxyl radical, OH, is the most abundant cometary radical…It is chiefly the presence of this radical that leads to estimates of the amount of water ice sublimating from the comet nucleus.
The thing is, hydroxyls are not often found as free radicals in and of themselves on asteroids OR comets, not in remote sensing or by fragment samples. Their presence in the first place is difficult to explain except as a constituent of volatiles, including -- but not limited to -- water and ammonia ices. It could easily be (and is sometimes theorized) that the hydroxyls originate from clays or hydrated minerals that are broken down and sublimated at high temperatures (much the way the combustion of some hydrocarbons release water vapor as a byproduct).
Which is the biggest flaw in your source: the "dirty snowballs" objection is a strawman, and the rest is mainly just scientific ignorance.
What the public didn’t realize, he said, was that academic science, too, was becoming a business. “There are scarce resources, you need grants, you need money, there is competition,” he said. “Normal people go to the edge to get that money. Science is of course about discovery, about digging to discover the truth. But it is also communication, persuasion, marketing. I am a salesman. I am on the road. People are on the road with their talk. With the same talk. It’s like a circus.”
This is indeed true and is a serious problem with many of the more abstract fields -- particularly psychiatry and cosmology, where hard data is hard to come by and sophistry is a way of life.
Astronomy, however, isn't generally of them, and the study of comets tends not to have this feature since it's so much easier -- and more important -- to locate and track them than to figure out what they're made of.
