First, the firmware update didn't remove support for a feature, it explicitly blocked certain user space software. It forced consumers to use Sony's PS OS rather than an alternative like Linux.
Second, it helps establish precedence that hardware vendors can have control/part ownership of hardware after you purchase it. Gone are the days where the computer you purchase pre-assembled is your own. Now vendors can apparently control what you decide to do with hardware that you purchase. Sony isn't alone in this, Microsoft has been moving towards this for a long time, and Apple is probably the worst offender, but they are joined by most hardware vendors at this point.
It's anti-consumer behavior. It probably shouldn't even be legal, but yet corporations can get away with it, so they continue to do it since it aligns with their best interests (barriers to competition).