Many specious claims without evidence have been made about left handedness, that it will lead to “learning difficulties”, “mental problems”, “criminal behaviour” and other bunk, Other claims (which have been refuted or questioned) claim that left handed people are susceptible to schizophrenia, autism mental illness, etc., or that left handed people are more likely to be pedophiles.
There are different claims for the cause of schizophrenia and also its triggers. One of the things which triggers schizophrenia is stress (emotional or physical). Forcing a child to use the wrong hand will creating stress, which could make schizophrenia more likely to happen, not less.
Regardless of whether any of these things are proven or disproven, linked or unrelated, isn’t it best to leave children alone? Let them use their naturally preferred hand, teach them techniques specifically designed for their preferred hand, and not abuse them with forced hand switching.
Yes, forced hand switching is abuse: physical, mental and emotional. Left handedness is as natural as sexual orientation and gender identity. If you consider “aversion therapy” imposed upon LGBTQIA people to be abuse, why are you not also against “aversion therapy” imposed upon left handed people?