Your point of view sounds reasonable but it does appear that you (like many other slashdotters) regard pornography as being harmless. There is much evidence that contradicts such a belief.
I revert to an illustration I'm quite fond of: if you know a drink is poisonous, how much of it do you drink? To add to the illustration, if your kids want to drink it, do you allow them to only as long as you can supervise them and watch them do it?
Now clearly we are coming from entirely different viewpoints on this issue. Just know that for those of us who consider pornography to be objectively dangerous/harmful, the quantity, setting, or myriad other factors are of relatively little importance. I'm not the type of person who supports legislation to "fix"
our problems for us (the only government I support is God's Kingdom) but I do empathize with where this mother seems to be coming from, i.e. there's a danger, help me protect my children from it.