How do you respond to a Christian who quotes the Bible about homosexuals?

Here is a Jewish perspective, which is very helpful:

Leviticus says absolutely nothing about gays, since the concept of sexual orientation was completely unknown in Biblical times. Leviticus 18:22 has been used to persecute gay people, but it actually offers multiple interpretations. Even the most traditional interpretation only talks about sex, not sexual orientation.

More compelling is Leviticus 2:18, which says:

וַיֹּאמֶר ה׳ אֱלֹוקים, לֹא-טוֹב הֱיוֹת הָאָדָם לְבַדּוֹ; אֶעֱשֶׂה-לּוֹ עֵזֶר, כְּנֶגְדּוֹ׃

And the ETERNAL G-d said: 'It is not good that the man should be alone; I will make him a helper for him.

The Hebrew Word for Helper in this verse is ezer (עזר) which is masculine. Now it is true that masculine Hebrew nouns can also be used generically to include the feminine, but if this "helper" was only supposed to be a woman, we would expect the Word ozeret (עוזרת). We can conclude that this verse could apply to male helpers or female helpers.