No corporation shall acquire directly or indirectly, the whole or any part of the capital stock of any competing corporation doing business in this state, nor directly or indirectly acquire the franchise, plant or equipment of any other competing corporation doing business in this state if such other corporation be engaged in the same kind of business and be a competitor therein, where the effect of such acquisition of stock, franchise, plant or equipment may be to substantially lessen competition or to restrain trade or competition in the state, or any community thereof, or tend to create a monopoly of any line of commerce and will be inimical to public welfare. This section shall not apply to corporations purchasing such stock in payment of an indebtedness, and not using the same by voting, or otherwise, to bring about or attempting to bring about, the substantial lessening of competition. Provided, however, that fire and marine insurance corporations may own stock in other insurance companies and may be licensed to do business in this state, or authorized to continue business in this state, but the state insurance commissioner may refuse permission to any company to be licensed in the first instance or he may subsequently revoke the license of any company if it appears after notice and hearing that to permit one insurance corporation owning stock in a competing corporation to continue to do business in this state would be injurious to, or contrary to the public interest.