While I respect all of the work that aides do (I was a CNA once), you have to remember that your education and license is above theirs, therefore, they cannot look at what you're doing and make the determination that you need to be doing something else.
Everything that they do is within our scope of practice so you have to look at it as though we can do everything they do plus a lot more that they can't. They are there to take the work that can be done under a certificate so that we, the RNs, can do the nursing stuff that they cannot. If you have a minute, yeah absolutely help out your aides and ultimately your patients, but if you do not have a minute, you cannot let them bully you into questioning your priorities.
Ignore their comments but also stand firm that you are the RN. Remember, you went to school to learn how to prioritize nursing care. Between taking someone off the commode and prepping to transport a patient to OR, you as the RN can clearly see which one is the priority. Next time feel free to tell your aide yourself that their priority is not yours right now. Of COURSE be respectful about it; the better respect you and your aides have for each other, the better your lives at work will be.
tldr; ignore their comments, help out when you can because it will be better for everyone, but don't let them bully you into forgoing your priorities as an RN.