That's a problem of the companies. GPLv3 contains no fundamental changes in the freedoms it gives and requires to be uphold - it just clarifies some things explicitly (in particular that tivoization is explicitly forbidden, where before it was some legal gray area) and gives better compatibility between the GPL and other FOSS licenses.
You explicitly wrote about GPLv3 in your post above. For GPL software in general, your claim is surely true. But I see no reason why GPLv3 might make a difference (except for the few rare cases where tivoization might play a role) over GPLv2 here.
Given they were using the LGPL before, which means they were already using GPL software, it means they are already in conflict with their legal department.
It is a difference (also to the legal department) to use GPL/LGPL software (say, GNU/Linux) or develop (or even release publicly) software that uses components/libraries that are under GPL/LGPL. I think pjmlp was implicitly only talking about the second scenario.
You made a low-effort comment that GPLv3 is the only no-cost licensing option for Qt. But that's not a "fact"; it's still available under LGPL, which makes your comment untrue. That's why you got downvoted.
It looks like you didn't. Qt is still available under LGPL. Both the blog post itself and the top comment here (which is also the thread you responded to) spell that out.
If that's the only point you intended to make, then fine, say that. But you didn't. What you said was that anyone looking for a no-cost option for Qt now has to use GPLv3, or they can pay for a commercial license (and then complain about getting downvoted). These are not the same thing.
The former is something to have a discussion about.
The latter is verifiably untrue, and has massively wasted time for someone not wanting to see the lie get repeated or go uncorrected.
EDIT: Apparently stating facts how many companies see GPLv3, regardless of the license contents, hits a nerve with the downvote squad.