Feel your pain. I brought this up on day one with my current therapist. I find it really stressful to end a relationship, and I'm upfront about what makes me feel triggered and defensive. A therapist is someone that you should be able to gradually open up with, and feel comfortable sharing deep scary stuff with, without fear of push back. It can be traumatising/retraumatising being dismissed or shut down.
I'm sure my last therapist had poor self awareness. It really angers me now that she would tell me counciling isn't right for me, after I had decided to stop seeing her. I can't believe that she would hold that belief as a councillor/therapist. I think she didn't have the guts to say she wasn't able to help me any further.
They're only human, and it is likely "just a job" to some.
I really like my current therapist. He does trigger me sometimes, but he takes his time listening, and doesn't usually rush his remarks. He even says sometimes "I just need a minute to think about what you've just said", and he does feedback really positively. It's really helpful.
Think there's no way to ensure. I'm looking for a therapist I really like, that seems tough enough to hear me out, and not get defensive.
It's not your job to make your therapist feel comfortable