I would change the title of this article to «Is being a wimp killing your career?»
Being a spineless coward is very different from being empathetic. Your whole argument rests on the assumption that empathy and other traits have a continuous pressure on a person’s demeanor. That’s silly. If you are an empathetic designer, you will fight for outcomes that better serve your users (unless you’re a wimp). And of course that you will fight for your team and for the greater good of the organization, if you are a leader (unless you’re a wimp). And keep in mind that leaders are always empathetic.