Deli meats and cold cuts are VERY VERY high in sodium, and treats is too non specific for me to comment on. Sounds like the dog is getting what is paramount to junk food. This dog will have health problems and probably a shortened life span, her vet bills are goig to be high - she should get insurance now.
Wanna help out, go get a pamphlet on Natural Balance. Quality dog food may cost more, but dogs eat less, poop less and are healthier, costing less in the long run.
I expected by dog to have died by now, he is a bull mastiff mix and at 14 years old is still going strong and surprising everyone at how good he looks.
I feel for that dog. Your friend should be put on notice that what she is doing is paramount to neglect.

I know she means well but it's killing with kindness. She is very giving and loves to spoil - my kids and dog love visiting her too! Maybe I'll even suggest a homemade dog food.

I don't know if the diet is contributing to the pain while defecating so I will address each issue separately.

A diet in processed meat and "treats" is certainly deficient (and most likely dangerously so) in essential nutrients, the most serious of which is calcium and the other electrolytes. Having imbalances in electrolytes can lead to serious muscle and heart issues not to mention bone health.

Pain while defecating can be indicative of overly firm stool, parasites, or anal sac disease, or rectal disease, or prostatic disease in males.

There are ways to homecook balanced nutritious meals (or feed raw) but the point is that the diet must be balanced over time. Feeding an occasional cold cut isn't going to harm their health, but a diet exclusively made up of it (with treats) certainly is extremely harmful.

You friend needs to take the dog to a vet for a full evaluation and to tell the vet about the dog's diet and ask for suggestions. He may need bloodwork to evaluate calcium, phosphorus, and sodium levels, and to check for kidney or other organ damage as a result of this diet. The "dirty backside" warrants a fecal check for intestinal parasites in the least.

Lunch meats and hotdogs are full of nitrates that can be very damaging to a dog's digestive system. People food, if one is careful can be a great diet -- my last dog (large breed) lived a healthy life for 16 years, but we limited what we gave her. She got dog food and table scraps that were limited to all low/no salt meat scraps, fruits and veggies and anything else we had left-over that was healthy.

Our current large breed pup gets only dog food simply because our kids are grown and gone and we have very few left-overs.