I love brainstorming with people. It is fun to bounce ideas back and forth and watch them grow into something useful, imaginative, and creative. Some people can reach creative and imaginative conclusions in their own heads without the help of others, but my first tendency is to think out loud. This means my wild inner thoughts sometimes burst forth before they are refined or even politically corrected (gasp!). I have found this to cause trouble if I am not careful, and in a similar way Peter finds himself admonished in Mark 8 when he speaks forth falsehood.
It is often said that Peter was bold, quick to speak, and showed forth other related characteristics. This is what we see in Mark 8:32. Peter rebukes Christ in a move that is clearly heretical for the true church as evidenced by Christ’s response. It is true that Peter receives the Holy Spirit and reverses course at a later date, but at this point Peter still had his mind set on the things of man (v 33). He understood Jesus to be the Christ (v 33) or the anointed one sent by God; however, when Christ plainly revealed the full earthly aspect of that mission (to suffer, die, and to rise after three days), Peter allowed his initial reaction to be the external explosion of his inner thoughts and feelings. Peter is not rebuked here for how he responded. The problem was that his thoughts needed to be altered. Peter was like the blind man from a few verses earlier who could “see people, but they are like trees, walking.” (8:24)
The subsequent rebuke from Christ reveals a crucial aspect of the Gospel. It cannot be compromised. The true church throughout history, which most definitely includes our day and age, will stand upon Christ as He revealed Himself. To leave out any aspect of what Scripture reveals about the person and work of Christ is to side with Satan in his attempt to deny God and thwart His kingdom.