I found a link to some research when I was looking for more about this case. It was about men who use prostitutes. It showed that there sexual preferences became more 'extreme' over time - those that started off looking for vaginal sex developed a preference for anal sex. I'd imagine the same can be shown with porn use over time - that those who start out with an interest in one man one woman sex over time seek out multiple penetration.
Not all men are looking at violent porn or strangulation or humiliation, but I do think regular use of any porn has some impact. This isn't page 3 or magazines, it's hard core videos online.
There is a desensitisation effect - over time it takes more for someone to reach the same level of arousal. When you spend your time looking at women being doubly penetrated and having men come in their faces it's hardly likely to improve the way you view women is it?
I'm doing a u-turn on the decision to exclude the evidence as well. I went and read more about the case. I think that it could have been legitimately excluded, but not when the judge allowed the following exchange:
From BBC site
Mr Lickley (prosecution QC) asked Tabak whether his motivation in killing Miss Yeates was sexual.
"What's the difficulty in accepting it is sexual?" he asked.
"Is it because there are other sexual elements to what happened?"
Tabak replied: "There were no other sexual elements."
Mr Lickley asked: "Is the holding of her throat sexual in your mind?
"Did you derive sexual gratification from holding her throat?"
Tabak replied: "Definitely not."
"Were you sexually aroused when you were holding her throat with your hand over her mouth?" Mr Lickley asked.
Again, Tabak replied: "Definitely not."
That, to me, is pretty much signing off on perjury.