Once you become of age and are over 18 years old you have to live for you and I'm sure this isn't the first time they have not liked who you dated and it won't be the last parents often feel that no one is good enough for their baby and will do anything to get that person out of their child's life no matter what age you get they will always try to run your life, it is up to you to let them know that you are no longer a child and if you live on your own it's time for you to live for you and make your own way in life. They are going to have to allow you to make your own decisions, mistakes, and future. I'm pretty sure the only way they would be content is if you were alone. Tell them that even though you respect their opinion the final decision is yours to make and that you have to live with this guy they do not but try not to say it in a disrespectful way.
Your parents are going to worry about you until the day they die and will always have an opinion about not only who you date but the decision you make as far as your life is concerned, it doesn't mean you have to listen to them just hear their opinion and advice and then tell them "Thank you for your advice but I think I will learn that on my own", they will know that you heard them and they will no longer say anything maybe they continue to say this because they feel you are not hearing them sometimes you have to pretend you hear them in order to keep the peace. You are going to have to sit down with them and tell them that you appreciate their concern but they have to allow you to live your life and make your own mistakes and that you are not chosen your boyfriend over them but you would expect them to be there for you and support you no matter what you choose to do.
They are still trying to run your life as if you are a child still and you are not, also tell them that if they truly loved you they would love you no matter who you a re with and they are putting unrealistic expectation on you to listen to what they say or not be in their lives and that isn't fair to you, they may never accept your boyfriends and then you would be fighting an uphill battle all of your life so you should put your foot down now and not wait any longer if you truly want to be happy you have to life for you not your parents.