I think their point is that you're not taking a principled stand by stealing. If it matters enough to you to "boycott" the company, walk the walk and don't play the games by any means.
A person only buys physical copies of non-Nintendo-made games which run on Nintendo devices from people reselling legally-distributed copies (legal in the US with the first-sale doctrine, which unfortunately doesn't apply to digital copies). The person plays those games by ripping the files and running them on third-party emulators. The person publicly states that they boycott Nintendo the company and that they play non-Nintendo-games made for Nintendo consoles. Resellers might or might not spend their money on more Nintendo games.