I think you are saying people should not fear God, is that so? I'm confused what you are saying, Matthew is referring to fearing God. Just curious.
"Fear", as it is used in this particular passage has something like nine possible meanings, depending upon the context of the intent and emphasis of the surrounding and supporting words. And the monstrous failure of almost ALL of our English translations is that they seldom attempt to accurately relate the author's intentions, but rather just try to cover the meaning with one of our English words. And, often they fail woefully.
For instance, you can possibly fear many things... to some extent, or some degree. You fear lions and tigers. But you also may fear speaking in front of crowds. Or, you might fear flying. Or, you might fear an upcoming evaluation at work. And, here is the most relative one..... You feared your father when you had to face up to something you knew he didn't want you to do. BUT....... were you REALLY morbidly AFRAID of your father? Maybe yes, maybe no........ only you, in your skin, at that moment. can truly say. It's similar with each of the Bible's writers.
So, you see, the Bible has hundreds and hundreds of words like this that cannot ever be truly understood in all the subtle nuances of the original languages they were written in... UNLESS you, yourself are a native reader, and are looking at the original texts... and have a pretty good idea of how the author thinks and writes.
This is a little tough on us because most of us are left having to trust that the translators didn't let any of their own views and biases influence the manner in which they chose a particular meaning (of sometimes ten or fifteen possibilities) to apply to the singular word they happened to be translating at that point in the text. And, let's face it, do you honestly think ANY human can do that in an unbiased way? Not likely.
Thus, we pray for guidance, and frankly, we kind of have to put it all together in relationship to all of the rest of the Bible. This is why we cannot just read a few hundred pages of the Bible, and think we know what's what. Mostly, I think it is reliance upon that guidance of the Holy Spirit, and the rather difficult ability to REMAIN OPEN to learning more and deeper meanings every month, or so. The biggest key, I think, is to NEVER get yourself wedged into a position of thinking you know it all because you happen to understand a passage a certain way today. Tomorrow may dawn completely new for you.
I believe the most dangerous Christian is one who thinks God has given them "all knowledge".