Furthermore, Rashi (Bereishis 29:11) tells us that Eisav sent his son Elifaz to kill Yaakov! He wouldn't do that if he cared for his parents, for how would they feel if Elifaz carried that out?
And in this week's parashah (26:35), it states, ולרבקה ליצחק רוח מורת ותהיין, that Eisav's wives caused Yitzchak and Rivkah much distress because they worshipped avodah zarah to spite and to anger Yitzchak and Rivkah. Eisav didn't stop them. He honored his father with his deeds and with his speech, but the primary aspect of honor was lacking.
Yet, Eisav was rewarded for his kibud av v'eim. One reward was the strength and power that was passed over to his grandson, Amalek.
Reb Yehonoson Eibshitz zt'l writes, "Amalek's power comes from Eisav's merits because he honored Yitzchak. As it states (22:28), עשו את יצחק ויאהב, 'Yitzchak loved Eisav...' But it was all בפיו ציד, from Eisav's glib tongue, because Eisav didn't honor Yitzchak in his heart. He didn't do anything from his heart, only with his mouth..."
And since his honor was only through deeds, we can cancel and revoke Eisav's merits when we honor our parents with our deeds, with our speech, and with our thoughts, too. This perfect form of kibud av v'eim will annul and cancel Eisav's merits for his imperfect kibud av.
Additionally, Reb Yehonoson Eibshitz says, if we serve Hashem with all our heart (for any mitzvah), we annul Eisav's strength. Eisav's good deeds were only in action; when we serve Hashem with our heart, mind, and soul, it cancels out all of Eisav's credit.
Reb Yonoson Eibshitz laments the fact that we lack heart, especially during tefillah. He writes, "I talk about this matter all day and all night, and I don't stop speaking about it: A Yid should serve Hashem with his heart, with kavanah. He shouldn't serve Hashem by rote, due to custom... especially tefillah, because tefillah is avodah shebalev, the primary service of the heart. But due to our many sins, people got into the habit of mumbling their tefillos... The lips and tongue move by habit, and his heart is thinking about business and other matters. Woe to him for the day of judgment! When he is old, there won't be more than two or three proper prayers that he said with kavanah his entire life... The same is with kriyas Shema. How many weeks and years pass, and we don't say kriyas Shema, the three parshiyos, with a whole heart, without interspersing other thoughts?! Woe to us! This empowers our enemies because we are in galus under Eisav's domain, and their merit comes from their forefather [Eisav] whose power was with his mouth (בפיו ציד). If we serve Hashem with our hearts, he loses his strength. But if we will be like them and only serve Hashem with our mouths, Eisav's merit remains in its place."
The Yaaras Dvash adds that this is the intention of the pasuk (27:22), והידים יעקב קול הקול עשו ידי, "The voice is the voice of Yaakov, and the hands are the hands of Eisav." This means that if all we have is the יעקב קול, the voice of Yaakov, such as the sound of Torah and tefillah, but it is without the heart, then עשו ידי והידים, Eisav still has power over us. When we serve Hashem with our heart, Eisav's merit will be canceled, and Amalek and the goyim won't have any power over us.
