Personally, I've been involved in character optimization on forums for about 8 years now. During that time there have definitely been some optimizers who have not been nice to others at all, and frankly, there have been some non-optimizers who aren't very nice either. However, I think you will find, if the chance is given, that most of us are here because we enjoy the game and like to communicate with others that enjoy the game too.
Optimization isn't a fringe part of the game. It's built right into the rules. The PHB is giving you optimization advice consistently as you read through it (example: The "quick build" advice for each class). This is because the game is a mix of storytelling and challenge, and some basic optimization allows you to meet that challenge with success. Avoid it if you like, but removing optimization from the visible 5e forum makes no more sense than removing any other rules based discussion.
The general forum-etiquette I have always followed, and I daresay the vast majority of optimizers follow is this:
1) Provide guides or advice on clearly labelled threads so they can be found by those interested in looking at them (Example: My own "Treantmonk's guide to Wizards")
2) Provide advice or feedback on any thread where optimization advice is requested. (Example: Someone asking for advice on a Wizard build to fit into a stealth-based party)
3) If optimization advice is not requested, don't provide any. I always figure if someone wants advice on this topic, they will ask.
4) Participate in the community as a whole, by posting experiences/opinions that are not optimization advice (as I'm doing right now)
5) Don't dump on anyone, period. Honestly, Optimizer/Non-optimizer says nothing about our personality. I'm an optimizer, but I'm certainly not a power-gamer looking to overshadow anyone.