No need to sugar coat it. If that's what you really think, then write it clearly: "Hey guys! Hey my fellow hackers! That poster is a... is a... CORPORATE SHILL!"
Most of my audience aren't hackers, at least not in the sense I think you mean.
And the poster is likely not a corporate shill. "Shill" has connotations of undisclosed association and intentional deception, neither of which are things I'm accusing anyone of. I don't think there's any reasonable expectation of disclosing associations on a pseudonymous forum. And I don't think most posters here are being intentionally being deceptive--they probably believe what they're saying, as most people will go through great mental calisthenics to believe what they're doing isn't harmful.
The late-stage capitalist ideologies held by much of this forum are extremely harmful, but I don't need to accuse people of malicious intent to say that. People can intend the best and do great harm.
In general, HN users can be trusted to take the side of corporations over humans in the vast majority of situations.
EDIT: Downvoting without giving reasoning just lends further credence to my point that their views are based in selfishness rather than reasoning. ;)