Unions are market participants in this case attempting to enforce cartel structures on an entire industry for their paying constituency - no better than the RIAA. Regulations should break this but not at the cost of consumer protection - cost cutting, not safe etc.
My issue is not with the unions, but with the governments that afford them special favors. If it weren't the unions in this case (Is it even?) it would be the taxi corporations themselves.
I think it is therefore important to focus the criticism not on unions but on the politicians themselves who try to get in Ubers way.