See yesterday to understand today. ... People are usually partial to their own. Therefore, in asserting superiority or quality, it's wisest to start from the bottom, and let other people make the discovery that what you have is great. This is an aspect of humility. It's not self-degrading, or sloppy; it quietly recognizes quality, and lets everyone come alongside at his own chosen pace. And while you pay attention to other people, and don't aggrandize ourself, soon they'll be more willing to listen to what you have to say in return.
What does this have to do with writing? In writing, there are choices: You can write with little or no opinion or feeling, keeping your offensive line so far back it's almost invisible. You can write with extreme opinion, guns blazing before you wake up in the morning, and long after you've gone to sleep at night.
There is a middle ground; one that embraces the value of having opinions, without making them paramount or prisoner. Blunt, badgering dogmatism that's not backed up well rarely convinces anyone—then, neither does lackadaisical laissez-faire. Have good reasons for your opinions (awards, global recognition, multiple experiences and certifications), but be kind about them. Don't pin people to the wall until they agree with you, and if you don't agree or care about something, don't malign those who do. People will listen and endure those who are well-educated geniuses, authorities, and wealthy, even if they are belligerent, malicious, and despicable; but people will respect someone who is kind.
Bolstering your image with sarcasm, dogmatism, and pedantry doesn't work in the long run. Not only do you lose respect (if you even had it to begin with), you lose the possibility of mutual care and relationship (not necessary in many occupations, but always nice). Respect, you can live without; lots of people do. It's a lot harder to live without friends.
Write with humility, earn yourself respect. Don't make claims that aren't supported—have reasons for what you say. And next time you read (hear) someone claiming that "My ______ is the best," think about Jim Beam and his award and smile silently, because you know that just saying it doesn't make it true, but you don't have to fight it.
*Note: there is a difference between opinion and belief.