It looks like you're in damage control mode and should treat it as such.
The damage is that you did not establish respect AND a good relationship with the individual when you met them and/or when the team formed. This is something you need to learn to see coming in the future when someone is an obvious threat.
Note, you don't want to "expect trouble" in the future, you want to build a better relationship and establish respect to keep trouble from happening.
Control the damage by:
Damage Control: Relationship:
Immediately getting to know more about the person and finding things that you like about them. Don't try to make them think you like them or you'll lose more respect, just genuinely look for things you like and/or respect about them and remember those things when you look at them or talk with them etc.
Damage Control: Respect
So, to stop the team demoralizing arguments, you're going to have to simply stop arguing. It may be hard to see, but the argument is not about the topic at hand, but more about your ability to control the situation. He/She's saying you cant control the situation and is proving it with their unproductive actions.
You're feeding the monster by giving it attention when it's bad. That's your primary fault here.
Another way to look at this is, by arguing at all, it says that you feel the need to justify yourself, therefore proving your team member's view that his/her age or title or whatever makes them superior to you causing even more damage in terms of respect.
I agree with the other poster in that you're getting baited in and your adversary is winning when you get involved.
Here's a simple strategy you can use that has these benefits:
- you still get valuable information
- you remaining in control
- you do not justify yourself
- you don't demoralize everyone else
- Conflict starts over an idea. Recognize when it has become a conflict and that if so, it is not about the idea but about emotions. You will need to learn to recognize this earlier and earlier. The earlier you can tell the slight vocal intonations or word choices, the easier it is to stop.
- Ask to hear the point of view of the person. Listen during this time to weed out the conflict from the information that might actually be valuable to you.
- Make a decision right then and there based on the information you have. If no decision is to be made, skip this step. But either way, don't justify yourself. If you're insulted, just ignore it. If you're asked "why" you can easily say "I heard what you had to say and took it into consideration, but this is the way we're going". He/she will definitely try to bait you and/or demand that you justify your decision. Don't. Don't justify and don't fight. Sometimes they will give good information and you will agree with them. Sometimes they wont. Even if you agree with them, Don't Justify.
- Move on to the next point with a gentle persistence. Probably ignoring more comments.
After a couple of times he/she will get the message.
Also, If at any time during the process they start to raise their voice, be prepared to remind them to "please act professional"
Don't forget to build the relationship or this will just create a cold war.
Of course this is a short reply to a complex topic, but hope it helps.