Chizuk Emunah (Pt 2) Under the Microscope: Chapter 14

Matthew 10:40, Jesus is made to say to his apostles, "He that receiveth you receiveth me, and he that receiveth me receiveth him that sent me." By this expression the Christians are reduced to the necessity of believing that Jesus and his apostles are identical; and as they are taught that three make one, they ought, by parity of reasoning, to deduce the inference from the present passage, that the trinity, with the twelve apostles, make altogether one unity.

I assume this is a response to a bad Christian argument. Presumably, the argument states that those who accept or reject Jesus accept or reject God the Father, hence, Jesus is the same being as God the Father. If that is the Christian argument, then yes, it is a bad argument for the Trinity.

The point here is fairly simple. Jesus was sending his followers out to recruit for his movement. He was telling his apostles not to worry if people reject them. It is not you that these people are rejecting, but God. This is also taught in Berakhot of the Mishnah. "A man's messenger is as himself." Rashi also noted this in his commentary on Exodus: "He who seeks the face of an elder is as if he receives the face of the Divine Glory." Rabbinic tradition recognizes that someone who rejects a messenger rejects the person who sent the messenger. That is all that Jesus is saying in this verse.