It's ridiculous for him to think that other people should help him just because he doesn't manage his time well.
It's funny for him to think he doesn't need to come to class because he's out looking for a job.
この場合、次のような言い方ができますよ。
ーIt's ridiculous for him to think that other people should help him just because he doesn't manage his time well.
「彼の時間の管理が下手だからと言って、他の人が自分を手伝うべきだと思うのはおかしい」
It's ridiculous to ... just because ... で「…
だからと言って、…するのはおかしい」と言えます。
ーIt's funny for him to think he doesn't need to come to class because he's out looking for a job.
「彼は就職活動をしているからといって、授業に出る必要がないと思うのはおかしい」
It's funny to ... because ... でも「…
だからと言って、…するのはおかしい」と言えます。
ご参考まで！
カナダ 
