I don't think the flag wars will be the first thin an investor would be thinking of. It will act as a secondary reason keeping them from investing more or simply demotivate those who were on the fence regarding investing into STEEM.
Some investors may post once in a while (at least comment) or maybe they will have friends or people who they are fan of becoming casualties of toxic behavior. If they see good authors leave or post less due to these downvoting related toxicity, the investors will hold STEEM at a lower valuation.
I do believe that SMTs and reducing free downvotes can help the situation massively.