If you think rats are less intimidating for passengers then I invite you to test your hypothesis by walking around an airport with a rat on a leash and a dog on a leash, see what gets the most response.

Have you seen the average bomb dog? is not a labradoodle...

And google ethiopian rat, is not that ugly/scary like black rats and others.

I'm not sure how to compute the average bomb dog but Labradors are in fact very common sniffer dogs:

http://www.usatoday.com/news/military/2010-09-30-1Adogs30_ST...

Lots of German Shepherds as well and plenty of other breeds. No, the're not 'doodles' but a pack of angry Jack Russels isn't a pic-nick either. The point is that people are somewhat used to bomb sniffer dogs because they associate them with the dogs they already know. With rats they will also associate them with the rats they already know, and that association is not going to be a good one.

That rat looks like this:

http://www.viewchange.org/videos/africa-bomb-squad-rats

So, you'll be testing your rat-on-a-leash in a crowded airport ---->>> there

and meanwhile I'll be

<-------- over there.

I hate being trampled by screaming tourists.

Well look at this way: if you don't like the scanner then you're getting a very intimate patdown, which depending how you take it could end with a surprise cavity search.

Now the rat doesn't sounds that bad does it?