I am doing the taxes of my parents. He is disabled. She is claiming his care home costs(over 10k) meaning no DTC. How do I override and still be able to netfile?

You can remove the disability amount by changing the answers to the questions on the Disability Amount screen. 

Use the Find button to search/select the option for Disability Amount. Change the answer to the question: Do you have a severe mental or physical impairment in 2017? to No on your father's return. This will remove the disability amount and keep the full amount of the medical expenses.

Doesn't doing this make them ineligible for the care home costs deduction?  CRA document RC4065(E) 18 says you must have T2201 filed with the person, which means you have to indicate that the person is disabled in the return, right?

Thanks,

No. The disability tax certificate remains on file with CRA. Removing the credit within the software by indicating No to those qualifying questions has no bearing on eligibility for other disability-related credits.