Ok, I take your word you did not personally say that, but other posters have, and your argument seems to be that the laws are enough protection for worker's rights. Am I wrong? If the laws are enough, then it's one more step to "so unions are not needed." So I apologize for conflating you with other posters who said unions are no longer needed, but I hope you can see how it was an easy mistake to make.
As for the slippery slope -- yes, everything is a slippery slope, so we have to be diligent that things we care about don't slip off the table.