Nadiine, your OP was great. You were very clear that you were confused about a position held by a Calvinist because it doesn't jibe with the whole of scripture. I know he wasn't advocating Universalism. I was merely pointing out that Universalists use that verse in 1 John to defend their view. The Calvinist understanding or interpretation of that verse is problematic as well, since that verse does not say that Christ died only to pay for the sins of the elect. The verse clearly says that He died to pay for the sins of the world. He's making a distinction about who makes up the "world" that scripture doesn't support.
Here's the entry Thayer's has on the meaning of the original word that is translated as "world" in 1 John 2:2. The Calvinist view takes that last possible definition and it's problematic because it doesn't gel with what the whole of scripture declares.
G2889
κόσμος
kosmos
Thayer Definition:
1) an apt and harmonious arrangement or constitution, order, government
2) ornament, decoration, adornment, i.e. the arrangement of the stars, ‘the heavenly hosts’, as the ornament of the heavens. 1Pe_3:3
3) the world, the universe
4) the circle of the earth, the earth
5) the inhabitants of the earth, men, the human family
6) the ungodly multitude; the whole mass of men alienated from God, and therefore hostile to the cause of Christ
7) world affairs, the aggregate of things earthly
7a) the whole circle of earthly goods, endowments riches, advantages, pleasures, etc, which although hollow and frail and fleeting, stir desire, seduce from God and are obstacles to the cause of Christ
8) any aggregate or general collection of particulars of any sort
8a) the Gentiles as contrasted to the Jews (Rom_11:12 etc)
8b) of believers only, Joh_1:29; Joh_3:16; Joh_3:17; Joh_6:33; Joh_12:471Co_4:9; 2Co_5:19
Part of Speech: noun masculine
A Related Word by Thayer’s/Strong’s Number: probably from the base of G2865
Citing in TDNT: 3:868, 459
The Calvinist understanding greatly changes other key scriptures. For instance, apply this understanding to John 3:16-17.