They don't actually think anyone who suggests IRB approval is very mean and very bad, that line really isn't the thesis statement. If you read a bit further I think you'd be less annoyed by it.
In this case, it functions as a hook; it's there to give you a slight chuckle before diving into a long and relatively dry informative article. It's some clear sarcasm makes you evaluate the supposed assertion made - that people who push for IRB evaluations are meanie-heads - and challenges any preconceived notions you might have of it being a simple "this is good" or "this is bad" thing either way because of course it's not that simple. This invites the question to the reader: if it's not as simple as that, then how is it actually?
Of course, if the tone doesn't land and you read it as a factual statement - and, importantly, it's so distasteful that you immediately bail and don't read the rest of the article to see what it's actually about, and just assume it's a petulant tirade against IRBs - none of that works. If you're at all interested, I would recommend reading some Adam Mastroianni / Experimental History posts, as it has a very similar feel but plays to the strengths of the tone a bit better (IMO). This one [0] actually touches on the use of humor in scientific papers, and I think makes a pretty good case for why clinical language isn't necessarily a good thing.
[0] https://www.experimental-history.com/p/the-rise-and-fall-of-...