Part of my opinion is that we have several federal laws that protect employees from discrimination, so I guess I don't see how our unions are supposed to help in that respect....there are plenty of other constructs in place to protect for that.
We have laws here but proving you've been sacked or not got promotion because of discrimination is very hard. The union helps you fight your case, otherwise it's you against the company who will have lawyers. You can have lawyers too if you have the thousands of pounds it will cost, the unions provide a solicitor who is an expert in employment law to represent you.
If you are being picked on at work it's good to have someone who's on your side.