Mother in law and babysitting... 🙅🏻❌🚫

 My husbands mother wants so badly to babysit but I'm having a hard time deciding if I am comfortable with it or not. When my husband and his siblings were younger his mother was dating a meth head and she knew he was a meth head!! My husband has told me stories of him and his sister in the kitchen at only 8-9 years old cooking meth for this guy and those innocent children thinking they are making cookies... this man raped my husbands sister. My husband would tell me that there would be people strung out on hardcore drugs in and out of their home all night. My husband tells me I'm being mean for not being ok with it but I'm honestly just not comfortable with his mother watching my children... Any advice ladies? What should I do? Let the past be the past?