TL/DR: Fast food should not be considered for bulking, there are better alternatives.
You have an issue with the categories you are thinking in. It's not only healthy vegetables vs. unhealthy fast-food.
First of all I'd doubt that fast-food will have any beneficial effect on the body. Of course, when working out, it's possible to gain some muscles when eating fast-food, but this is not because, but despite the fast food.
[...] he will increase his body fat. As a result he will obtain obvious muscles faster than someone who is trying to eat healthy.
The person eating fast food will mostly gain fat, not muscles and therefor maybe look bigger, but this is not due to more muscles.
Having said that, eating healthy and gaining are not mutual exclusive, but you have to consider the following
- To bulk (gain weight - muscles at best) you have to be in a caloric surplus, i.e. take more calories than your body would normally need - at least on training days
- It is possible to eat healthy and be in a caloric surplus
- To gain muscles you have to take a considerable amount of protein (about 2 g per kg bodyweight)
- There are many sources of good protein that are healthy (or at least not unhealthy): Lowfat quark, cottage cheese, chicken breast
- You can supplement protein with whey and the like (look for quality products)
- Nuts and seeds have a high caloric density, but are considered quite healthy, opt for them if you need some extra calories
- Whole grain unsweetened cereals are great, too. Many fibers, still good source of calories.