Absolutely a deal breaker!
My last boyfriend loved Layla... for the first few months. He started getting more and more tired of her, and JEALOUS of her... It started that she couldn't sleep on my bed if he was there, then she couldn't sleep in my room period. THEN she wasn't allowed on the same floor as him

She was scared of him and whenever he came over, she ran downstairs and stayed under the couch until he left. I hate that I let that happen. He broke me down so much to believe nobody else would ever want me, he was the best I'd ever do and I might as well settle. But, I never considered ever giving up Layla even though he pushed me to do it constantly. I gave up nights with him to stay home with her.
The big eye opener came one day when he was leaving my house in the morning, all happy and cheery, and he opened the front door, and Layla came running upstairs, tail wagging, happy to finally see me... but he wasn't gone yet. His demeaner did a complete 180... he raged and called her a "Cocky b****" and stormed up the stairs after her... she ran behind the couch. He grabbed the corner of the couch, threw it across the room, and slapped her. I threw him out of my house SO FAST and told him never to ever step foot in my door again. I cried and hugged Layla, and was late for work because I was so traumatized by it. He didn't come to my house again, and I ended the relationship for good, after a year and a half together.
My boyfriend before him didn't like Layla, but tolerated her and never did anything mean. I didn't like that either. He made me feel stupid for how much I doted on her. I vowed I wouldn't date another guy who didn't absolutely love my dog.
Well, Layla's new daddy is everything to her that I am

He wouldn't think of hurting her. He didn't bat an eye at the expense of her spinal surgery, and even cried in the exam room thinking about maybe never getting her kisses again. He is everything I have ever wanted in a man. He didn't grow up with animals as part of the family.. he had a dog and a few cats that were given away when they were too much work for his parents. He now says he can't imagine ever living without a dog.