Why did I mention all this, any c

Good Friday - what is BAD? Why do we call it as Good Friday when Lord Jesus was crucified in the cross? Isn't that should be called as Bad Friday? This is one of the questions that many of my non-Christian friends ask and some of the Christian friends too.
I had an argument with one of the Professor in a stress interview with 600+ students in the auditorium witnessing me literally sweating from head to toe and blabbering to his questions and this is how it went...
Prof: Do you think 13 is a unlucky number?
Me : No, it's not.
Prof : Have you ever heard people saying this thing?
Me : Yes, I've heard it. Some of the western flights doesn't have a seat numbered 13.
Prof: and no 13th Floor, 13th room too. Many more.
Prof: Do you know the significance behind it?
Me : No, I don't.
Prof : Paul, you are a Christian right?
Me : Yes, I am.
Prof : Have you ever seen the painting of the Last Supper?
Me : Yeah, the one by Leonardo-Da-Vinci. I've seen it.
Prof :That's right and his master piece was the painting of Monalisa.
Prof : Can you tell me how many disciples were with Jesus in that portrait?
Me : Blank........ ( calculating....12 disciples +1 Jesus so 13. But wait, was Judas there? "Bulb at the right moment". Yes he was there) Totally there were 12 people. Oh no, sorry, there were 13 of them. ( By this time I know I am pulled down :-( )
Prof: Well, what happened to Jesus after that?
Me: He was crucified.
Prof : Now, don't you think that 13 is an unlucky number?
Me : No it is not.
Now the professor got a bit screwed up with me and he goes like this.
Prof: Okay, tell me what is the purpose of Jesus coming into this world?
Me : To save mankind.
Prof: Well, did He accomplish His purpose?
Me : Yeah, He did.
Prof : No, He was killed in the middle.
Me : Yes correct. There can be no salvation and forgiveness without a blood shed. Now, it was His blood that saved you and me.
Prof: I've been with my Bible for 18 long years and I know what it is all about.
(Being a Professor in English Literature that too in a Christian institution, he obviously has read the Bible)
Me : He defeated the satan on the cross and He rose up again on the third day as prophesied.
..........
I end up with this because we have the answer now. If you want to know the results of the interview, please meet me in person.
Yes, we call it as Good Friday because that is when Jesus defeated Satan on the cross, taking our sins, transgressions, shame..... all over Him and saved us once for all. Now we are saved by His blood.