What is the significance of the vicious treatment that Christian and Faithful receive at Vanity Fair in the book Pilgrims Progress?

Vanity Fair is a Fair of evil and a metaphor for sin in
this work. Everyone at the Fair represents some sort of evil and opposition to God. When
the pilgrims arrive, it is evident immediately that an atmosphere of evil pervades the
Fair. The "Prince" himself (the devil) is said to pass through Vanity Fair, so
comfortable is he with all of the "vanities" that are sold there. The pilgrims stand out
immediately from the rest because they are good, but the people of Vanity Fair are evil.
The pilgrims will only buy truth, but truth is not for sale at this evil Fair, so the
pilgrims are cruelly treated. They are spat upon, jailed, tortured and Faithful is
killed at the stake.

Faithful is a Christ-like figure. He
stands for the truth and defends God, but when a jury of your peers consists
of:

Mr.
Blind-man, Mr. No-good, Mr. Malice, Mr. Love-lust, Mr. Live-loose, Mr. Heady, Mr.
High-mind, Mr. Enmity, Mr. Liar, Mr. Cruelty, Mr. Hate-light, and Mr.
Implacable

What chance does a
righteous man have? Faithful is condemned. The significance of all of this is that
Pilgrim's Progress is a Christian allegory and the plot and
characters all stand for some part of Christian theology. Faithful remains "faithful" to
the truth, as did Jesus, and he is condemned to die because of the sin of others, not
any sin of his own.