Don’t be less opinionated. Lowering your standards is like poisoning your own well.
The question should be “how to avoid sounding like an ass?” Opinions aren’t the problem, lack of awareness and sensitivity towards others maybe.
There are correct contexts and methods for everything, learning to recognize and adapt to these are imperative for social survival.
Having opinions however is a sign of a restless mind. An arrow of longing so to speak. What is crude and obnoxious while young may flourish into insightful passionate interests given time and reflection.