Torah sages are perfected by means of the unlearned masses
See Shabbat 88b. To "turn the Torah leftward" signifies a preponderance of judgments; see paragraph 128.
The Torah causes harm to the sage according to the share of ugliness that inevitably exists within the sage's soul (small as it may be).
The Torah, like an "expanding glass," inflates all parts of the sage's soul, the good and the bad; thus, the sage's inner ugliness, small by nature, also expands, and the harm becomes very great in proportion to the Torah that sage has studied.
The relationship between the sages (talmidei hakhamim) and unlearned masses (am haArets) is not depicted here in the usual one-sided way (sages are called to teach and direct the simple masses) but as two-directional. As the sages teach the masses and move them forward, so the masses also rectify the sages. This is in keeping with Rav Kook's overall view, in which each segment of the Jewish people makes a beneficial contribution to the general advancement of all of the other segments, and in which each group has its shortcomings that must be rectified (in particular, by the influence of the other groups; see paragraph 21). It must be noted, however, that Rav Kook lacks the reverence for the common people, which was widespread in some ideological teachings of the time. Beyond doubt, simple people, like all other segments of Jewry, have their merits and their positive influence on others, just as they have their own abundant flaws, which they must rectify under the teaching of others. Accordingly, the rectification of the sage furthers the spiritual advancement of the common people.