cognitive dissonance and treat the cute little calf and big lump of steak as completely separate and unrelated

Oh yes this! There are so many people out there who cannot fathom hurting an animal and I know of people who will not eat meat bought directly from the farm. For them, meat "comes from the supermarket". Maybe it is a coping mechanism.

I eat plenty of meat and love it, but if I thought about the whole thing for too long, I could easily go down the Vegan pathway

Same here, but when I actually thought hard and long about it consumerism was the problem for me. Not vegan/not vegan or meat/not meat. The problem is shops that sell us the idea of never-ending supplies, even if it is vegan organic hummus.

I think humans would not have evolved as much in terms of brain power without the meat and fish part of the diet though

True, but then they had wild meat. Today we overeat ourselves on meat from sick animals. And as you rightly said, all those diseases only came about in our modern era of fast food, sick animals, and herbicides/pesticides.

Thank you so much for the thoughtful comment!