"Spots they are and blemishes, sporting themselves with their own deceivings while they feast with you." (2 Peter 2:13b) I can imagine Peter harked back to memories of Judas, being "one of the twelve" (Matthew 26:14), sitting in as Jesus shared things with them that, to this day, no one is privy to.
"That He might present it to Himself a glorious church, not having spot, or wrinkle, or any such thing; but that it should be holy and without blemish." (Ephesians 5:27)
This is what we're getting at. It doesn't matter how rosy things look, there's always someone out there who is a thorn but doesn't know it. Or if they do, doesn't want anyone else to know it. The word acanthous means "having thorns". Roses, regardless of beauty or fragrance don't take too kindly to being handled. Not sure where I was going with this metaphor but maybe you get the idea. As opposed to anacanthous. That means "without thorns". Solomon's song (2:1) speaks of "the rose of Sharon". I've read it refers to the love Jesus shares with His bride (it does), of which we all are part. As we get closer to Him, the thorns begin to tell. Each prickly place in us has its corresponding mark on His brow. It's truly a privilege to learn about the deep places in us we never knew were 1) there. And 2) full of weeds. Any number of passages from the scriptures could we pray to God in looking to have Him replace the weeds (and spots and thorns and blemishes) with His way of being and doing things.
"He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before His angels. He that hath an ear, let him hear what the Spirit saith unto the churches." (Revelation 3:5-6)
"In that day sing ye unto her, A vineyard of red wine. I the Lord do keep it; I will water it every moment: lest any hurt it, I will keep it night and day. Fury is not in me: who would set the briars and thorns against me in battle? I would go through them, I would burn them together." (Isaiah 27:2-4)
There are a couple of interesting correlations inherent to the multi-ingredient parallels in these paragraphs. The word "blot" comes from a root meaning "unprotected" and "bare". I suppose, as "vulnerable" is a synonym, you could throw that in there. Look at the above passage. God is helping Himself to the "vineyard of red wine". That's the Bride. The group of people who genuinely love Jesus and wouldn't do anything to hurt Him. Those whose names, as it says in Revelation, will not be blotted out of the book. And yet, anyone who'd do otherwise, anything less than what is required to retain a line in the guestbook of Heaven, is truly the "unprotected". Peter refers to those in our churches who have flown in under the radar. One of the parables of Jesus speaks of "children of the wicked one" (Matthew 13:38). Earlier on in the chapter, it would seem even the angels express shock at finding those in our churches whose hearts aren't right with God, to put it politely (see Matthew 13:24-30). See, things are serious all the time. And we all have the capacity to be used of "the wicked one" to do things, however subtly, that prevent God from getting done what He wants in the body. Bareroot roses have to be planted. After planting, the more God prunes your (and my) unruly parts, the deeper our roots grow in Him. Life is chock-full of metaphor and allusion and parable. But it refers to the deeper things of spirit that cannot be observed from without but must be walked in as Jesus showed and proved.
"Lord, who shall abide in Thy tabernacle? who shall dwell in Thy holy hill? He (and she) that walketh uprightly, and worketh righteousness, and speaketh the truth in his (and her) heart." (Psalm 15:1-2)