Maybe try having a serious talk with them about why it bothers you when they do that, and how you wish they would behave. Try not to sound accusatory. Talk about how it's affecting you rather than what's wrong with them. Be honest about your feelings, and about how the bullies behave. Try to get them to see everything from your point of view, while keeping in mind that they also have their own reasons for the way they behave, and that they're just trying to help. I hope you find my answer useful and it that it helps you out.
Ask them to and express your concerns to them. However, you state that your parents apologize to avoid confrontation, and you are wanting your parents to fend off bullies for you ie. avoiding confrontation. If you can't rely on those around you then you must rely on yourself and find your own way to overcome your situation, whether that is by talking to other people with authority or confronting the bullies yourself.
Unless these bullies are physically harming you or doing something to ruin your reputation (rumours etc) then their impact is only what you decide it to be. Bullies are just bored, insecure, immature people. They act that way because they lack the knowledge to be any different.
Often, open and honest conversations are a good way to express feelings and ask for support. If it proves to be difficult to have that with your parents, I experienced creating a "structured" environment to be helpful to not get caught up in emotions too quickly. What I mean by structure is that you announce that you want to talk to them. Either they have enough time right away or you make some kind of appointment, but to my mind, it is helpful when you are all doing nothing else at the moment except having this conversation. Moreover, it might be useful to lay down some ground rules such as "I am going to explain to you what I want and why I want it and I am going to express how I feel about it and why it is important to me. Please do not interrupt me while I am speaking. When I am finished you can tell me how you feel about what I said and I ask you to be open with me. It is important to me that nobody is judged or hurt in this conversation." or something similar. Essentially, expressing exactly what you want, need, expect and how you feel and explicitly ask others to listen can help an honest conversation. This may sound very formal, but for me, it has been helpful when asking for support and talking about topics that hurt me. A reason for parents to avoid conflict may also be that they do not know how to step up or act. Maybe it is helpful to find ways in which they can support you, together. I really hope this was helpful in some way. Wish you all the best!
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Related Questions: How to get my parents to stand up for me against bullies instead of apologizing to avoid any confrontation?