It's only not a high risk situation if they are in fact honest fishermen. If they were drug smugglers, I would expect them to also carry weapons. Boarding seems risky to me.
It's something routinely done, with ample ability to defend themselves against a single speedboat. They can always shoot a missile at the boat after it starts shooting at the coast guard; the outrage is that that was the first thing.
It's only not a high risk situation if they are in fact honest fishermen. If they were drug smugglers, I would expect them to also carry weapons. Boarding seems risky to me.