This is the real Mumbai. It's not always the cleanest or the prettiest, but it's what happens day to day. A small enclosed section of the Crawford Market has a number of butchers cutting up sheep and fowl. Is that..a tree stump? Being used as a cutting block? Sure seems that way.
Visiting on a Sunday is not a great time for the market, as many of the stalls are closed. Mumbai in general, on a Sunday, is pretty quiet and traffic is light. Great for seeing a lot of the city in the day, but not as great if you go to a market like this one and it's pretty quiet. Then again, some other markets were super bustling so check ahead of time when is good to visit a particular market.
In India I found that there was a bit of a mix in terms of friendliness towards photographers. I would say most people were fine and not bothered. This butcher, clearly was happy to have his photo taken. But some people, and as is the case in many countries, especially women, are not as happy about having their picture taken. So always ask/nod/pantomime some form of approval first if you're going to be up close.