This is dis-engenuous. One of the guests invited a tabloid reporter, did not appear to disclose the terms of the invitation to this person, and the result is predictable.
The ethical nuances here are lost because you have a sketchy company and an ethically challenged publication.
But in the same vein as the Mozilla incident, freedom of the press, nor freedom of speech...does not protect a citizen from another citizen.
If a muck-raking journalist wants to hide behind ethics to keep citizens from muck-rakin them, that's simply not protected by law or frankly by any real ethical consideration, other than the sense of moral proportionality that reflects their own behaviour.
It is a bizzarre point, but unfortunately its fundamentally correct.
The only "new" ethical consideration in this flap has to do with using specific information (presumably confidential company information) to bolster an attack. From what i've read, nobody suggested that this type of attack was only possible using a certain set of information.
Notwithstanding the distastefullness here, this is simply nothing that is not done in every major national election. So in that regard, the senator could equally send such a complaint to the DNCC.
What is actually the legitimate issue here is something much narrower: whether or not a malicious person would have the potential to abuse information that is not publicly available to do this.
That is very much a legit issue, but I'd be interested to see if the actual discussion would have been so bizaerre as to require this formulation. That would bring the company and its policies into the actual discussion in a way which simply articulating that low ethical standards swing both ways does not.
For example, a malicious threat would be something along the lines of "I know where you were last weekend at xx:xx" where this information would be used to extort or blackmail someone (eg, an affair etc). This type of threat would specifically hinge on the abuse of private information. Whether or not this was somehow allowed under any user agreement or employee policy is beside the point--its blatantly an abuse of implicit trust.
That is an entirely different type of situation that saying if "reporter X" is unethica, someone might very well do the equivalent of a classified-security clearance review of "reporter X" and articulate the findings in public. [1]
Needless to say, most people that look at this cannot distinguish the two cases, or if they can they are happy to disregard the reality of how the world works already.
The second issue is the idea of proportionality. In that when faced with some level or argument or counter argument, you dis-repscet the process of discourse and engage in ad-hominem. That is to say, in this case, retaliation with character assasination.
Again, I think this cuts both ways here. Being tone deaf and lacking in porportionality is a problem for ethically challenged startups--not doubt--but its also a problem with tabloids (see: uk phone hacking) and social media lynch mobs.
[1] If it meets the test of being legal and proportionate, its not really unethical by default.