I have been going through the samething with Buddy.
I said I would never have another dog like my last terrier who hated
other dogs and men. Made it really difficult for 16yrs. I did the same with
Buddy. I said he would love everything on this earth. HA HA didn't work!
He went to puppy classes, day care for awhile, is socialized with neighborhood dogs and plays with them, however anything new forget about
it.
Last Sun we went for a walk around my complex and an apple blossom tree
was in full bloom. Would you believe he went nuts, absolutely crazed because he never saw that before

He backed away from it like it would
bite him. I was laughing but annoyed that he could be so dumb. It's was then that I realized what
his problem was. He does not like change of any kind.
I thought about a trainer as well but to be honest I think this is just
how it is with this breed. They are very protective and you just need
to be aware of their problem and always be on guard.
Like people no two Yorkies are the same. It dosen't help either that
he's a teapot. More to restrain he's strong.
I was dissapointed about this as well and was upset but he's healthy,
loving to family and other dogs he knows. He's wonderful with my two
small granddaughters and loves them dearly.
I guess we can't have everything. I continue to talk him through strange
people, dogs and places hopefull that he will relax somewhere down the road.
Good luck.