And know that just as it is forbidden to slander one's friend, so is it forbidden to "slander" his possessions (see Rabbeinu Eliezer Mimitz in Sefer Yere'im). And it is very common, in our many sins, that one shopkeeper slanders the wares of another (and so, in other instances of the same kind), out of envy. And this is absolute lashon hara according to the Torah.
וְדַע דִּכְשֵׁם שֶׁאָסוּר לְהוֹצִּיא דִּבָּה עַל חֲבֵרוֹ כֵּן עַל חֲפָצָיו (י) אָסוּר לְהוֹצִּיא דִּבָּה {רבנו אליעזר ממיץ בספר יראים}. וְזֶה מָצוּי מְאֹד, בַּעֲוֹנוֹתֵינוּ הָרַבִּים, שֶׁחֶנְוָנִי אֶחָד מוֹצִּיא דִּבָּה עַל נִכְסֵי חֶנְוָנִי אַחֵר וְכָל כְּהַאי גַּוְנָא מִפְּנִי הַקִּנְאָה, וְזוֹ הִיא לָשׁוֹן הָרָע גְּמוּרָה מִדְּאוֹרַיְתָא.
And know that just as it is forbidden to slander one's friend, so is it forbidden to "slander" his possessions (see Rabbeinu Eliezer Mimitz in Sefer Yere'im). And it is very common, in our many sins, that one shopkeeper slanders the wares of another (and so, in other instances of the same kind), out of envy. And this is absolute lashon hara according to the Torah.