On every season of The Bachelor or The Bachelorette, a contestant approaches the lead, and tells them that another contestant is not there "for the right reasons". This means that that contestant may not be there to fall in love with the lead. This statement is insane for a just few reasons, so if you're planning to go onto one of these shows, don't be that contestant.
It's not normal to enter into a relationship with someone who is dating about 24 other people at the same time, and expect to immediately fall in love with them. What is normal is to go on this show expecting to have a new experience; maybe to travel, maybe to make some friends, maybe to promote yourself or your business, or maybe to fall in love. Being open to anything is the right reason to go one of these shows and as a contestant, you should be open to all of it.
Don't be the contestant that wastes their limited amount of time with the lead talking about other people. If something really does concern you, just wait it out. Often, the person who says something to the lead ends up shooting themselves in the foot. Personally, I would only say something if we were down to the final few contestants and someone who truly concerned me was still there. Even then I would only talk about it if my foundation with the lead was solid and if they asked me to say something.
I know that feuds amongst the contestants are often drawn out in order to entertain the viewers, so if you want to be that contestant who is known as the "Right Reasons Police", just know that you're probably going to end up in at least a few memes.