This is rather condescending, given that there are multiple studies showing the opposite of what you’ve said as well - the efficacy of inpatient treatment is a bone of contention between experts.

Inpatient treatment is a short term form of help and is meant to prevent further deterioration of the patient as well as instill useful coping mechanisms in a controlled environment. With such high incidence of suicide, if someone feels their condition is so bad that they need inpatient treatment, they should be taken seriously and at least evaluated to see if they are a good candidate for inpatient care.

From a study on 245 inpatients with BPD:

“The results revealed the following observations:

Large-effect-size improvements in depression, anxiety, suicidal ideation, and functional disability among patients with BPD (Cohen’s d ≥ 1.0) and non-BPD patient reference sample (Cohen’s d ≥.80).

Clinical deterioration and adverse events in no more than 1.1% of BPD and non-BPD patients on any outcome, with no difference found across cohorts.

No influence of BPD diagnosis on the trajectory of continuous depression severity

An association between trait emotion dysregulation and initial depression severity.

Surprisingly, rates of nonsuicidal self-injury and suicidal behavior, which are diagnostic criteria for BPD, were low. No patient in either group attempted suicide, and the prevalence of nonsuicidal self-injury was 3% for BPD and 1% for the reference group, with no overall differences (χ2=2.7; P =.10).”