Should I start speaking my mind tactfully at work right away?

Just keep being respectful. It always gets you far in life. :-) If it gets worse however, take it to your boss.

so quit

Make a diary of these incidents, recording as near as possible the exact words used, with dates and everything. Then read it over and decide if it sounds like a genuine issue or just you griping. (It might be a good idea to show it to someone outside your workplace - with no names of course - whose judgement you trust, and ask them for an opinion.) if you think your record shows that it is a real issue, take it to your supervisor and ask for advice in handling it.

Given you feel your co-worker has crossed a professional and/or personal boundary, and a private conversation has proved unsuccessful, speak directly with your Manager/Supervisor and ask for their guidance as to how best deal with the situation. If you feel it necessary, request a mediation meeting where both you and your colleague can discuss the matter with a neutral third party present.

just talk to your manager about it and let him do the talking

Just tactfully quit the rat-race.

Stop acting like a 12 year old. Just ignore them and do your job.