Why do people expect me to forget my late estranged mother who abandoned me because I’m “special needs”?

My late mom told me the brutal truth that the reason she left was because she didn’t want to deal with a “special” so called disabled child and wanted a normal child. It was uncomfortable and no longer wanted part of my life. Whenever I speak about my late mom that abandoned us, I either get cut off or people ignore me and walk away. My dad has scold me off for bringing up the past. He was a tough as nails man and he refused to let me sulk in pity or depression. He would me like, “Stop dwelling on the past and I’m not going to let you. Not on my watch. If you keep bringing it up, I’m going to be hard on you. Your mom doesn’t want you. Let her go already!!! You don’t need her.”
I feel like he was mean or too tough. I talk to someone else for sympathy because it’s hard to talk to my dad about my absent mom. My older half siblings flat out told me I need to stop bringing it up and they’re tired of it and Dad had be tough on me because I have been upset enough and sometimes it’s the only way to get me to listen and snap me into reality. They told me I’m an adult young woman and I don’t need to be crying over mommy and accept that she wasn’t a good mother. They said it’s okay to grieve, but move on.