AitchTwoOneOhTwo first of all, as a Catholic of Irish descent married to an NI Catholic, and with Irish Catholic family members in Scotland, I will never apologise for caring about sectarianism or mentioning it. Scotland does have a problem with it. You obviously don't like it and seem to feel some sense of shame about it- good. That's an appropriate reaction. It's how I feel about racism in England too.
Unfortunately though, it seems to be driving you to dismiss their experiences. I repeat- they are better qualified to talk about this than you are, because they went through it. They experienced bigotry from dunderheaded nationalists of the knuckle dragging, my country right or wrong, fuck everyone who isn't a Scottish Protestant nationalistic variety. Not just unionists. I don't know how much this still goes on, I hope not much, but that strain of nationalism has existed. Whether you like it or not. It has. Some bigotry has been informed by Scottish nationalist viewpoints.
That's why it's relevant to a discussion about whether Scottish nationalism has always been positive and healthy. Because I know it has sometimes led people to show bigotry towards outsiders. The people whose stories I mention weren't abused just for being Catholic, but also for their nationality. This means the prejudice against them was nationalistic as well as sectarian.
Oh, my family members aren't the only Catholics to feel like this either. I don't think the SNP are anti-Catholic, but some of the old school do. I found a bit of info on these links, not much, I think it's a view that's dying out now, as the SNP have done a lot to try and reach out to Scottish Catholics lately:
www.snptacticalvoting.com/2008/10/war-of-patrician.html
davidtorrance.com/letters-reveal-snp-crisi-over-bigoted-presidents-anti-catholic-diatribes-from-the-times-11-9-2010/
glasgowunihumanrights.blogspot.com/2011/11/glasgow-university-product-and-tory.html