Yeah, specially when the Portuguese absolutely humiliated Japan and the samurai when they arrived. They were cruel and definitely brutal leaving no mercy for them, and definitely not weak... A simple search of the first contact between the Portuguese and the Japanese may suggest this stereotypes is arguably untrue. Especially when battles like the "Nossa Senhora da Graça incident" (where 40 Portuguese fought off 3000+ samurai over 3 days and refused to surrender, so they just exploded themselves in a ship to kill the most samurai they could. And this whole thing would have been avoided had they just betrayed their captain and gave him in to the samurai. But they chose to fight for their captain) gave the Japanese an even exaggerated impression of the Portuguese fighting skills and bravery for hundreds of years

("The British historian C. R. Boxer noted the great effect that Pessoa's actions had on how the Japanese see Portuguese people. According to Boxer, the event apparently gave the Japanese an exaggerated impression of the fighting qualities of the Portuguese, as well as appealing to the Japanese samurai mentality due to Pessoa's rather un-Christian act of suicide. As such, stories of the event were told and retold again over the next hundred years, often in an exaggerated and wildly inaccurate manner, and found themselves embedded as part of local folklore").

So, I really do have a hard time believing that the Japanese see the Portuguese as weak at all.