(1) Any insurer may retain, invest in, or acquire the whole or any part of the capital stock of any other insurer or insurers or have a common management with any other insurer or insurers unless such retention, investment, acquisition, or common management is inconsistent with any other provision of this code or unless by reason thereof the business of such insurers with the public is conducted in a manner which substantially lessens competition generally in the insurance business or tends to create a monopoly therein.