First Amendment? As if.
This isn't a free speech issue. Their first amendment claim is part of a shotgun approach, where they're just throwing a bunch of legal arguments against the wall to see what sticks. (OK, sorry, mixing my metaphors.) Freedom of speech doesn't mean you can say anything you want to anybody you want at any time you want with zero consequences, and it's not blanket permission to do whatever you want.
And, ignoring the validity of the patent claim for the moment, this isn't actually a patent issue. Manufacturing and selling a product that infringes on somebody else's patent is a patent violation. Using such a product is not. The end users are not liable for the patent violation. The fact that MPHJ is bypassing the manufacturer and suing the end users is a pretty clear sign that they're just a bully threatening to beat up kids for their lunch money.
Of course, the fact that they're a non-practicing entity with nothing but a large patent portfolio and making all their money by suing the crap out of anybody they can was a pretty big clue, too.
East Texas, whatever other flaws or virtues it may have, is a typical venue for such suits because they have a track record of favoring the trolls.
MHO. IANAL. YMMV.