And this is exactly the way companies and other entities want you to think. If you actually dig into it, there are plenty of things that are said in a semi authoritarian manner that are not backed by law. These are done either out of ignorance of the law or intentionally to try and prevent lawsuits from even being filed but make no mistake, when presented in a court of law they would mean nothing. Most companies will say that rooting a device voids the warranty because it is easier than trying to say "Rooting and doing something stupid will void your warranty." For example, rooting the device and then having the device stop charging because the solder joints on the charge port failed will still be covered if the matter was taken to court. The reasoning is that there is no way rooting broke the solder joints. The manufacturer would have to prove that your modification (root) broke the solder joints before they could void the warranty. In reality no one would ever try to take HTC to court over an issue like this and also likely that HTC would warranty the device anyway. Just friendly advice, don't believe something simply because a sign or piece of paper says so. Most are not legally binding. That all said, should you root the device and then mess it up by doing something wrong, be honest and don't take it back claiming a warranty problem.Not being responsible for damage if you follow a dump truck too closely (traffic laws take precedent over that anyway) and voiding your warranty by rooting your phone aren't really anything alike. Of course the manufacturer can set their own (reasonable) warranty terms, if this was a real issue there would (probably) be a class action suit and rooting your phone would not void your warranty, and manufacturers and retailers would not be allowed to say that it does. Just like removing (or tampering with) the seal on an Xbox or PlayStation voids your warranty, or your water damage indicator showing that it was wet voids your warranty. Now, I'm not saying I'm with either side or that there aren't ways to skirt the issue, but there's really nothing to argue here. If the manufacturer says "if you do this, you're on your own" then if you do it, you're on your own.
Even Google tells you that rooting voids your warranty (and shows you how to do it)
https://developers.google.com/events/io/sessions/332704837