Not a fallacy

Are there exceptions or any points where the no true Scotsman argument is not a fallacy? 

Are there any times an appeal to tradition is not a fallacy? 

Are there any times where a slippery slope is not a fallacy? 

Well, grab your kilts and bagpipes, because we are going on a logical adventure!

First, let's tackle the "No True Scotsman." Now, this is usually seen as a fallacy because it's shifty. Like a Scotsman after too much haggis, it refuses to be pinned down. If you say, "No Scotsman puts sugar in his porridge," and then I point out, "but my uncle Shamus does," and you reply, "well, no true Scotsman does," well then, you’re just dodging the issue like an Olympic gold medalist in Issue Dodging. You're changing the standards to fit your argument. However, there may be rare cases where the "no true Scotsman" argument isn’t a fallacy. If, say, there's a conventionally agreed-upon and consistent feature of all true Scotsmen (like, they were all born in Scotland or have Scottish heritage), then you could potentially use it without falling on your fallacy face. But like spotting Nessie in Loch Ness, such cases are few and far between.

Moving on to the "appeal to tradition." This tends to be a fallacy because it says that just because something has been done one way for a while, it must be the best way. If that were true, we'd still be using carrier pigeons for mail and the world would be doing the Macarena. Almost horrifying to think about, right? Occasionally, though, tradition can embody an accumulated wisdom or practical advantage, so you might be able to invoke it without stepping on any logical toes. But watch out, because like a kilt in a stiff breeze, this can expose you to some shocks.

Finally, the "slippery slope." Normally, this is fallacious because it insists that one thing will inevitably lead to another with an almost Hollywood flair for the dramatic. "If we let people start wearing bow ties, then soon they'll be wearing top hats, and next thing you know, we're all living in a Dickens novel!" Sometimes, however, there may be a clear and well-supported cause-effect link that doesn't rely on wild speculation. Like if you square-dance on a greased log, you're likely to break out in gratuitous yodeling (or possibly just slip).

So there you have it. Even fallacies can have their rare day in the logical sun. Just remember, logic is just like haggis - sometimes it's incredibly satisfying, and other times it's just downright baffling.