Be able to defend your arguments in a rational way. Otherwise, all you have is an opinion.

The chess player who develops the ability to play two dozen boards at a time will benefit from learning to compress his or her analysis into less time.

Success is achieved by developing our strengths, not by eliminating our weaknesses.

Feeling is what you get for thinking the way you do.

...there are days when I feel I can do anything and days when I feel I can do nothing. But fortunately for those around me, neither sort occurs very often.

Be able to recognize many of the major constellations and know the stories behind them

Yes. The original argument is defective. Substitute the word 'male' for 'gay,' and you'll see the flaw: 'Male people cannot be normal. If everyone were male starting tomorrow, the human race would die out, so being male cannot be nature's intended way.' Or you could substitute the word 'female.' In either case, the argument makes no sense: Being male or female is perfectly normal.