No one is saying the concept of black holes was proposed by one or more unscrupulous theorists. Neither is anyone saying that the concept of a black hole is wrong. Still, there was a time not so many years ago in which no one had heard of the concept of an astronomical object with a gravitational field so high that even light, under ordinary circumstances, cannot escape. The question is, have black holes as of yet been established beyond doubt as being real? To listen to public discussion would suggest that many believe they have. Or, they do not exist? Again, no one is saying that. The question is, have they been proven, beyond reasonable doubt to exist?
Interestingly, NASA's Chandra X-ray Observatory has reported evidence pointing to the existence of a supermassive black hole in NGC 3115. By combining an optical image of NGC 3115 by the European Southern Observatory (gold-colored) with a recent x-ray image from Chandra (blue), produces a composite image Chandra suggests points to gas flowing back toward a supermassive black hole located at its center. Chandra candidly states, "This is the first time that clear evidence for such a flow has been observed in any black hole."
This scientist, albeit not an astronomer but a chemist, asks, "If a black hole does not allow light to escape, so a black hole cannot be seen directly, and if gas or other matter has never before been evidenced falling into one, wherein lies the bountiful proof necessary to establish their existence beyond doubt?" This question is not to dismiss possible indications black holes may in fact exist. A Harvard web site cited in the reference section below indicates, for instance, that matter being sucked into a black hole heats up to millions of degrees, emitting an x-rays and forming a tell-tale ring of brightness around such a structure. A list of such structures and images would prove most interesting.