Very odd.
These kind of decisions are entirely subjective but if you’ve provided the financial documents, evidence of ties outside Portugal including property and a business and you’ve got a history of meeting the conditions of previous visas then it’s difficult to see how they came to that conclusion.
I’d appeal and complain to anybody at the Embassy who will listen. Don’t underestimate the power of social media either. If the Embassy, the ambassador or any Portuguese official (particularly those linked to the tourist industry) have a Twitter or Instagram account then be sure to tag them while venting your frustration online. It’s a tactic that worked for me when my Mrs got a ridiculous French visa refusal. You hit the right person and all of a sudden the decision gets changed pretty fast!
Yes we are in the process of writing a letter supplying all the facts which I do believe it will be over turned. If not I will try your method or worse case scenario get a visa for another European country and travel via there or not go at all. This is not a must do trip and thought i would just tack it onto our UK trip.