I don't think that would make sense unless you could somehow accomplish it, not only without people knowing you were responsible for the murders, but that the deaths were murders at all. Otherwise rather than lowering the status of the group, you would probably make the public view them as noble victims.
Here we disagree on a matter of fact and expectation. Historically in cases where specific groups were the target of lynchings the resulting lowering of group status has been rapid. Even members of said groups lower their perceptions of their own status such that they avoid sending high status signals (acting as equal to the persecutors) and so making themselves the next target.
The same phenomenon can be observed in workplaces and other tribes within our culture, with respect to acts of humiliation, not death. The others in the tribe may view them as noble victims but victims are pitied, not respected. People, particularly ambitious people, will avoid doing things that affiliate them with the victim class. Status goes into free-fall.
I did mention 'one at a time' and 'in humiliating ways' so as to minimise any potential martyrdom bonuses. Something terrible happening once is an exception, a tragedy. Something happening a thousand times is a norm, the status quoe. In a certain instinctive sense it becomes legitimate.
The presence of humilitation and even the fact that it is a murder, not a valiant death in battle is also important. If the victims are raped, castrated and stoned then they just don't look as cool as if they charge into battle screaming "you may take my life but you will never take my freedom!" People at times have even placed a lot of stock in whether they are killed by the sword or by hanging - and for good status relevant reason.
Here we disagree on a matter of fact and expectation. Historically in cases where specific groups were the target of lynchings the resulting lowering of group status has been rapid. Even members of said groups lower their perceptions of their own status such that they avoid sending high status signals (acting as equal to the persecutors) and so making themselves the next target.
Can you provide any examples? I can't think of any cases where groups were targeted for lynchings where it's clear that their status fell as a result rather than their low status...
To break up the awkward silence at the start of a recent Overcoming Bias meetup, I asked everyone present to tell their rationalist origin story - a key event or fact that played a role in their first beginning to aspire to rationality. This worked surprisingly well (and I would recommend it for future meetups).
I think I've already told enough of my own origin story on Overcoming Bias: how I was digging in my parents' yard as a kid and found a tarnished silver amulet inscribed with Bayes's Theorem, and how I wore it to bed that night and dreamed of a woman in white, holding an ancient leather-bound book called Judgment Under Uncertainty: Heuristics and Biases (eds. D. Kahneman, P. Slovic, and A. Tversky, 1982)... but there's no need to go into that again.
So, seriously... how did you originally go down that road?
Added: For some odd reason, many of the commenters here seem to have had a single experience in common - namely, at some point, encountering Overcoming Bias... But I'm especially interested in what it takes to get the transition started - crossing the first divide. This would be very valuable knowledge if it can be generalized. If that did happen at OB, please try to specify what was the crucial "Aha!" insight (down to the specific post if possible).