Make light of

From Fresh Dictionary

English

Verb

make light of

1. ((idiomatic{{#if:|, {{{2}}}{{#if:|, {{{3}}}{{#if:|, {{{4}}}{{#if:|, {{{5}}}{{#if:|, {{{6}}}{{#if:|, {{{7}}}{{#if:|, {{{8}}}{{#if:|, {{{9}}}}}}}}}}}}}}}}}}})) To regard without due seriousness; to joke or disregard inappropriately.

   I wish you wouldn't make light of the matter, when it obviously means a great deal to him.