People will pile on, and the evidence that Verizon knows their technology can cause problems is already mounting. That they're pushing their products through without reviews or certifications could be seen as evidence of negligence or maliciousness.
What would be the cause of action? Why aren't the manufacturers of microwave ovens sued under the same cause of action?
If some product company (let's say, a router company) experienced some enormous increase in customer service and damage to brand image, I'd like to believe they'd eventually put quite a bit of money into finding out why they're losing money.
Could you imagine a world where a service rep has been instructed to ask whether a customer has any Verizon devices in the house? And to just give up, if they do, and blame Verizon? Would be terrible for Verizon's brand, pretty sure they're not ready (and probably don't want) to partition consumers who use internet-connected devices into pro-verizon and anti-verizon.
Your WiFi is slow ? Restart your computer, upgrade your operating system, clear your browser cache, move your router closer to you, buy a different modem etc. There is plenty of room for deniability that interference is the root cause.
Google is going to be pissed if their new wifi router doesn't work properly despite millions spent on testing, just because Verizon is screwing things up for everyone.