Sin is Sin
It's awesome to gain even the slightest insight into how Jesus viewed God's law. Not only is it concrete and never-changing, but he mentions that it doesn't matter what law God put forth, if he put it out there, there was a reason, and if you obey it, you will find Honor in Heaven. A sin is a sin, and by committing even the "smallest" of sins in our eyes is still viewed as a sin nonetheless in God's eyes.