Obviously people have different views on the topic of sex work, but Amnesty's approach seems atleast partly ideological and based on the idea that there can be a clear line between consensual and non-consensual sex work.
They say "You cannot enter this debate without recognising that it is often women and men who live on the outskirts of society who are forced into sex work. It may be their only way to earn a living. Decriminalizing their work does not mean condoning a world which leads them onto the streets. "
Others would say that they were not 'led', but pushed onto the streets, and therefore their work is not consensual and that paid sex work by its nature cannot be consensual. We could argue all day about the ins and outs of sex work, but the point is that Amnesty have clearly taken a side on a very contentious issue.
However, there is no 'pragmatic approach' defence for repeatedly tweeting 'Trans Women are Women' The slogan effectively says "Women must accept gender oppression and give up the language they need to protect their rights".
You can't claim to be protecting all human rights if you are espousing an ideology that limits the human rights of women.