"Aquarium Advice say"
Fish-in cycling can be done safely and easily, if you employ an effective technique. Unfortunately, there is a new wave of fishless cycling advocacy that has a tendency to demonize fish-in cycling as being some sort of cruel and difficult process, when in reality, it has been and will continue to be the industry standard for decades.
Believe it or not, fish-in cycling should not be an ethical concern like it is often made out to be. Often times, those that protest it have little actual experience with it, apart from a possible disaster story from their past or regurgitated preaching on the subject.
There are some common misconceptions on how people regularly get their tanks started. A person with several tanks most likely did not fishless cycle each of them, if anything they may have cycled the first one, or first few, but usually by that time the fishkeeper has a good enough understanding of the process to transfer some established filter media into the new tanks, which also technically makes this process a 'fish-in' cycle.
LFS advice can be sketchy at times, but not all the time. There is a reason why some privately run LFS are successful, and it is usually because they know what they are talking about. Granted, their stocking ideas may differ from the general accepted things you find on the net, but what do you expect? It's their business to sell you fish, so don't expect them to talk you out of buying things. I do not believe that any ethical business would advise you with the intent of harming your fish so that they can make more money off of you later in medications and other things.
Fishless cycling is a good thing, and if you don't feel like you can manage the responsibility of doing a fish-in cycle, then I suggest you go that route. But if you are like me, and don't want to stare at a barren tank for a month or two, then take the red pill and follow me down the rabbit hole.