What would you prefer instead? That they not hire these 50 people at all?

I'd prefer that they adopt a sane and reasonable growth strategy that doesn't depend on pump-and-crash cycles. There's a certain pernicious idea in business in general and in startups particularly that your worth is in large part how many people are working for you (I've heard multiple people answer "hey, how are things going" with "we just hired five people!" and my blood runs cold) rather than the efficacy with which you are achieving your goals.

(I'm a little less sympathetic in the case of engineers, who are an in-demand resource and so their opportunity costs are less, but the opportunity cost of your support people is higher and the recovery from the problems that that failed explosive growth phase cause is much worse.)

Is it any worse than some lumbering giant laying people off who've been around for twenty years, because the business model of 20 years ago doesn't work anymore?