I am saying that Jesus Himself is the fulfillment of the law. What He did, What He said, What He established is our law, and it is superior to and a fulfillment of the law of Moses. Again, "You have heard it said ____ (old, false understanding), but I say unto you ____ (true meaning)" is Him literally correcting the boundaries and understanding of the law of Moses, and it is binding upon everyone.
His entire life is why we do not live under the law ourselves. His coming freed us from it. To again quote part of an anaphora belonging to the Ethiopians (useful here, as they are the most outwardly 'Hebraic' in character of all the apostolic churches), "Let us not be circumcized like the Jews, for we know that He Who had to fulfill the law has come."
He did not commit blasphemy, so this is immaterial.
And the Jews were quite simply wrong about that.
So what? A great deal of things that are 'Biblical', when placed into the hands of people who don't know what the heck they're talking about, lead to horrible blasphemies like placing God Himself -- Jesus Christ -- under the control of the Mosaic law, as you have done. Such people and such thinking does not respect the New Testament, wherein the promised Messiah of the Old Testament came to us as Jesus Christ, Who revealed Himself also to be the Son of God (see: the Transfiguration, His baptism, etc.), and was persecuted, tried, and put to death on the cross on account of that. And you are correct that doing so was simply following the law of Moses as they knew it. My point, however, is that their knowledge of whatever principle they had is absolutely obliterated by Christ Himself. That's why what He says goes, and when He says that He has come to fulfill the law (Matthew 5:17), we take it seriously and count it as fulfilled in His life, death, and resurrection.
The old law has passed away, but Christ Who lives forever has established the way for us. There is now no recourse to what was done before Him, no matter how much we may venerate the patriarchs of the OT (which we do in the traditional churches), because again what He did -- what He preached, what He established -- is what we follow.
Yes we follow the higher law that He preached in the sermon on the mount. We also follow the two great commandments of LOVE which He preached:
(New Testament | Matthew 22:36 - 40)
36 Master, which is the great commandment in the law?
37 Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.
38 This is the first and great commandment.
39 And the second is like unto it, Thou shalt love thy neighbour as thyself.
40 On these two commandments hang all the law and the prophets.
However we are no longer under the law as we are under grace yet we should NOT sin:
(New Testament | Romans 6:1 - 15)
1 WHAT shall we say then? Shall we continue in sin, that grace may abound?
2 God forbid. How shall we, that are dead to sin, live any longer therein?
3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
7 For he that is dead is freed from sin.
8 Now if we be dead with Christ, we believe that we shall also live with him:
9 Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
10 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
11 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
12 Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof.
13 Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.
14 For sin shall not have dominion over you: for ye are not under the law, but under grace.
15 What then? shall we sin, because we are not under the law, but under grace? God forbid.