In very very simple terms.
One person uses pejorative language, acts on it = not a big problem.
Thousands, nay, millions of people the world over use pejorative language, act on it, normalise it, ingrain it into social structures = pretty big problem.
Now, as individuals, challenging millions of sexists is tricky. Challenging hundreds very difficult. Challenging one, whenever encountered, is easy. And the more people who challenge that one ignoramus, the easier it gets for others to challenge those with offensive views.
Now, here comes a more complicated bit. It isn't easy to change one thing by 100%; it's usually easier to change 100 things by one %.
It's called "aggregation of marginal gains"; I hope the OP has mentioned that the word "bird" when applied to a person, a woman, is offensive, and not just to one woman, and that it's not without consequence, because if millions of people have that attitude well, well, women would be second class citizens throughout the world.
So, any update OP?