Your comment struck a note with me, not because of your snide tone, but because you did make me wonder what the legitimate definition of "fucking" is. Is a penis necessary for intercourse? Can lesbians really "fuck"?

Most dictionaries define "fuck" in this context as an act of sexual intercourse, which by extension is defined as "Sexual contact between individuals involving penetration, esp. the insertion of a man's erect penis into a woman's vagina."

I would therefore conclude that we are both wrong in this case. A penis is not necessary for fucking, although penetration may be necessary to qualify. I will edit my comment accordingly and encourage someone with better perspective to elaborate on this.