Excellent questions, all of them, and deserving of serious answers. I'll take a stab at a few of them.
It is an unchallengeable tenet that watching porn is good for one, or even a nation?
I'll assume you meant this as a question ("Is it.." rather than "It is...) and answer it thus. It is, of course, not an unchallengeable tenet. In one sense, it is perfectly fair of you to challenge that presumption. And really, to also be fair, the burden of proof of harm should rest with those who would ban or restrict or regulate it, as it should with all things that someone wants to ban or restrict or regulate.
But in a more fundamental sense, challenging that tenet is not really the issue. Society already permits to individuals many, many things that are not good for individuals over the long run (especially in excess) or possibly for the nation as a whole - cigarettes, Big Macs, candy bars, alcohol. It seems to me that to be consistent, we ought to judge whether the negative effects of a thing outweigh the positive aspects. And where the evidence is unclear, it seems best to me to err on the side of individual freedom.
Can a person's head be filled with graphic images of sexual activity, at the same time he is in a state of hyper stimulation, without lasting effect on the way he views women, sex, and the priority of pleasure?
Apparently, yes. To wit:
Voluntary exposure to pornography and men's attitudes toward feminism and rape
The Journal of Sex Research; New York; 1997; Kimberly A Davies;
Volume: 34
Issue: 2
Start Page: 131-137
ISSN: 00224499
Abstract:
A study was conducted to determine whether men who rented more X-rated videos displayed more negative attitudes toward feminism and if they were more likely to condone violence toward women than were men who rented fewer X-rated videos.
Full Text: Copyright Society for the Scientific Study of Sex 1997
[Headnote]
The effects that pornography have on men's attitudes toward women remains an issue of contention. Most previous researchers who have examined the relationship between pornography and attitudes toward women have used experimental studies or aggregate studies. Instead, I examined a sample of men who voluntarily viewed sexually explicit videos of their choosing in a non-experimental setting. I examined the relationship between these men's renting of pornographic videos and their attitudes toward feminism and rape. More specifically, the purpose of this research was to determine whether men who rented more X-rated videos displayed more negative attitudes toward feminism and if they were more likely to condone violence toward women than were men who rented fewer X-rated videos. In this article, I used cross tabulation to compare 194 men who rented X-rated videos of their choosing from a single pornography establishment in a large metropolitan county during 1988. The men were compared on their attitudes concerning the Equal Rights Amendment, a law against marital rape, and punishment for date rape and marital rape. No correlations were found between the number of videos a man had rented and his attitudes toward feminism and rape. These findings suggest that calloused attitudes toward women may not be generated by sexually explicit videos but are more deeply ingrained in our society.
Can we say that porn builds character?
I don't know. But again, even if it doesn't, neither do many other things made freely available to consenting adults. If not building character is the guideline we will use for determining what is and is not present in society, I suspect that we will find ourselves banning a great many things that we currently take for granted.