@mcc Recently learned that Einstein was pretty bearish on black holes also. In that case, it was because (IIUC) his process was often "Think about a possible model for how the universe works, think through the consequences of that model, test those consequences against reality..." And when he applied that reasoning to the gravitational singularities in the math he went "But that would imply there would be these... holes in space. We've been looking for thousands of years and we don't see any holes; where are all the holes?"
I can't remember if he lived long enough for astronomers to get back to him with "Well now that we know we should be looking for 'wild bullshit happening around nothing'... We turned our telescopes towards that and UH-OH!"