Been here and done this and have survived and earned the respect I amply deserved. First off, nasty remarks undermine teamwork and professionalism. You approach each individually, straight out tell them you don't appreciate not being given a chance to succeed and find this unprofessional and not to mention stressful. You ask to be given a fair shot as if they don't agree with HRs decision, they should broach HR about it and not punish you. This is the behaviour of immature cowards who are trying to sabotage your success to give themselves another chance at success. Always be polite and never make it personal as this will be perceived as weakness on your part. Then start recording notes, as if they have been approached yet continue, you now have a case to address with your boss and with HR at the same time so that communication is clear....always preface things with your understanding that teamwork is the key to success and that you are looking to make team work in your company because you know that leveraging this will contribute to corporate success. This way it shows that you have tried to resolve this yourself and given people a chance to choose positive change before escalating as you know that you have tried and if the behaviour continues are now aware that the resolution is beyond you. Don't take too long to approach higher ups as believe me, I waited two months before I said anything and in that time my blood pressure climbed dangerously high due to the stress and my boss did ask me why I waited as he believed the lapsed time contributed to the problem getting worse. Support was there my friend as you were hired because you are good and the higher ups know how to protect a good investment.
cheers