93% of the time in this situation, it’s because they don’t like what you represent, i.e., increased competition and decreased security, whether academically, socially, romantically, or professionally. Just you showing up activates this reaction in them; this is why you cannot take it personally. However, if pressed, they might not even recognize this in themselves, and might blame some faux pas you didn’t even realize you committed. The main thing is to show them you’re a human being and not an object that is displacing and encroaching upon them, and decreasing their relative value. You can do this by being humble and self-deprecating, not taking yourself too seriously, or engaging in playful, witty banter which serves to overcompensate for their negativity and insecurity in your interactions with them while simultaneously demonstrating that you are secure and not to be F’d with.