Should local languages ​​be allowed in a country, or should only the country's Official Language be spoken?

Should local languages ​​be allowed in a country, or should only the country's Official Language be spoken? I think the official language of the country should be spoken. Otherwise, unity and solidarity is interrupted and everyone tries to put their own language into practice. You will speak the language of the country if which country you live and which country you are a citizen of. This is it very difficult? (I would like to add that I am definitely not racist and fascist.)
Should local languages ​​be allowed in a country, or should only the country's Official Language be spoken?
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