The others have healed and made their peace. {Or so he hopes.} Grief is not easily overcome even for immortal beings.

{Everyone heals at different rates. Thranduil has been separated from the others. He lacks the comfort they give to one another.}

To blame an entire race for the doings of a few is foolish. Maedhros and his brothers, on the other hand, are guilty of many deaths. They slew their own kin. {He doesn't want Beleth to be blind to that fact.} You must realize there will be hurt no matter what decision is made in the end - and you cannot call anyone wrong.