If every person who brought a medical malpractice lawsuit were to have a meritorious claim, then every such plaintiff should win their case (simple norms of compensation and corrective justice would dictate this--uncontroversial stuff). However, if that were to actually be the case, you would likely hear the AMA screaming that the system is stacked against doctors--how can it possibly be a fair system if plaintiffs win every case?
Of course, if that weren't the case, if the plaintiffs didn't win every case, according to the premises set out above, that would mean some people, injured by medical malpractice, wouldn't be appropriately compensated--and we can all agree that that's bad, strictly on fairness and corrective justice grounds, as mentioned above.
Ergo, it seems actually not so bad that there are non-meritorious claims being brought to trial, so long as tort law is relatively good at weeding those out from the meritorious ones (which it does seem to be:
http://content.nejm.org/cgi/content/full/354/19/2024). In that case, non-meritorious claims are not rewarded, because a full airing of the facts finds that they should not be compensated; meritorious claims ARE rewarded; and the system looks fair because it has winners and losers on both sides.
Therefore, "loose lawsuits based on nothing" are not only a definitionally-necessary aspect of, well, our entire legal system, but also normatively important to maintain legitimacy.
As a more philosophical matter, you're sort of begging the question (in the strict sense, not the loosey-goosey sense of "raising the question"), by calling these "loose lawsuits based on nothing"--the trial and/or the legal system is what is charged with determining whether they are meritorious or not, know what I mean? You can't deny someone the chance to get their claim heard and ruled on by ruling on it in advance and finding it lacking--that's precisely what the court/jury are supposed to do at the thing you're saying they shouldn't be allowed to have.
Also, just as a note: the percentage of actual victims of medical malpractice (as determined by an independent panel at a later time) who do go ahead and file lawsuits is shockingly low--something like 12% (
http://www.iii.org/media/hottopics/insurance/medicalmal/). Given that statistic, I think it's ridiculously unfair to paint medical malpractice victims (and their attorneys) as uniformly greedy, stupid, and grasping, which I think is too often the portrait. Admittedly, there are cases that aren't meritorious, but I tend to think that A) very few of those claims are brought in bad faith, as a percentage of the whole; and B) the tort law system does seem to do a good job of weeding those out--which is precisely what we say we designed it to do: weed out the undeserving and compensate the deserving.