Sam,
As others have pointed out, while from the drowning Egyptians it would seem improper to celebrate, there other Gemaros that imply otherwise, so stop spitting out blanket issurim.
Here is the Gemara that Pekak referred to:
Megilla 16a:
אֲמַר לֵיהּ: סַק וּרְכֹב. אֲמַר לֵיהּ: לָא יָכֵילְנָא, דִּכְחִישָׁא חֵילַאי מִימֵי תַּעֲנִיתָא. גְּחֵין וּסְלֵיק. כִּי סָלֵיק, בְּעַט בֵּיהּ. אֲמַר לֵיהּ: לָא כְּתִיב לְכוּ: ״בִּנְפֹל אוֹיִבְךָ אַל תִּשְׂמָח״? אֲמַר לֵיהּ: הָנֵי מִילֵּי בְּיִשְׂרָאֵל, אֲבָל בְּדִידְכוּ כְּתִיב: ״וְאַתָּה עַל בָּמוֹתֵימוֹ תִדְרוֹךְ״.
Haman then said to him: Mount the horse and ride. Mordecai said to him: I am unable, as my strength has waned from the days of fasting that I observed. Haman then stooped down before him and Mordecai ascended on him. As he was ascending the horse, Mordecai gave Haman a kick. Haman said to him: Is it not written for you: “Do not rejoice when your enemy falls” (Proverbs 24:17)? Mordecai said to him: This statement applies only to Jews, but with regard to you it is written: “And you shall tread upon their high places” ( Deuteronomy 33:29).