Firing people is a natural part of doing business. Decision should be judged (morally) on the margin. If I fire 100 people, I haven't resulted in 100 people never being able to work again, I have simply shifted them to their next-best option.
That's not to say that terminations aren't a necessary part of doing business. The leaders just need to be very careful about managing the growth of a company in a responsible way.
The rest of your post is premised in the idea that firing someone is inherently immoral. It is not something that should be taken lightly, since there are big adjustment costs for both sides, but as I said before, it only moves a person to their next-best option. The action of firing someone shouldn't be viewed as depriving them of a job for life* (which is made up for by a virtuous company providing them with a job for life). The same argument applies to many other cases. A school teacher cannot say "if it weren't for me, these children would have had no education, see how valuable I am" because if it weren't for that teacher, someone else would have done the job.
*Here life = the average time a person spends at a company and the argument remains the same.
I don not claim that firing someone is immoral. I just say that I do not want to be fired, and I will prefer an employer that likely won't fire me.
I am German, maybe that explains a cultural gap between us - I wouldn't mind working within the same company (but not the same job!) for the rest of my life.