Oh well.....everyone has an opinion..including me.
Certain breeds and larger dogs usually get a reputation of sorts by many and unfortunately the reputation might not always be correct.
When I get that routine from some folks I will try and interject some humor and/or sarcasm. One of my favorites is when some ask if my GSD is vicious...I like to say "of course not' and then have her give me a kiss or lick my hand...followed by .."well, I think so or she could just be tasting me before she attacks and eats me".
There are many crazy notions out there mixed in with the good ideas...I have yet to hear the one about fixing a dog lest they become sexually attracted to you....that's a good one. I think I might have replied.." oh, no worries, as long as I eat garlic once a day, it wards off all sexual advances...."
As soon as I meet a crazy dog person, I immediately decide to just roll with their comments and perhaps humor them in a subtle fashion.
We are all dog experts....including me