What is “かたいことばかりは言えないがだ”?

Question

This is from the long-running anime Sazae-san. Let me set up the situation. A young couple is at a public telephone. The woman is calling her parents, telling them that she's at her female friend's and will get home late today. The viewer sees that this is a lie (since she's with her boyfriend and the guy is sticking his tongue out). Then suddenly, a stranger out of nowhere （波平）just snatches the phone from her hand and seems to be giving the parents a lecture. Below is the transcript:

(The woman) もしもし？
(The woman) 今　カズコんちにいるの。

(The woman) 帰り　遅くなるから。

（波平）いかん！ (snatches the phone)
（波平）あなた　お母さんですか？(already talking on the phone)

（波平）失礼だが
（波平）お宅の教育は　間違っている。

(The woman's mother, on the phone) あの　ちょっと
(The woman's mother, on the phone) 主人と代わります。

（波平）いや　そりゃ
（波平）かたいことばかりは言えないがだ。

The anime is here (starting at 10:30): http://www.dailymotion.com/video/x46ojrm. Watching it is going to be essential in understanding the situation, I think.

Now my question is, what is 波平 saying to the parents? It seems to me that he says to them that they are raising their girl wrong (お宅の教育は　間違っている)? The last part I simply don't understand: "かたいことばかりは言えないがだ". Something about them being too conservative? Also, what's with "がだ" at the end? Doesn't look correct grammar-wise. (This script comes from TV feed so it should be correct). This is all weird: I thought he would tell the parents the truth (that they were being lying to), and not go at them like this (perhaps I misunderstand the scene?).

Answer 1

The last part I simply don't understand: "かたいことばかりは言えないがだ". Something about them being too conservative?

Yes, かたい (I suppose it's 堅い) means "firm, rigid" thus can describe someone is (too) conservative or moralistic.

Also, what's with "がだ" at the end? Doesn't look correct grammar-wise.

Yes, it's grammatical for copula だ (である, です etc.) to attach to particles to close the sentence, since it's able to connect to everything except conjugable words (用言; verbs, adjectives and so-called "auxilliary verbs"). This construction often doesn't have direct translation into English, but functionally, it makes sure that a sentence ends there (because when you pause after a particle, the hearer couldn't know if a verb comes later or not). Pragmatically, it often conveys speaker's assertion or emphasis on the phrase before.

うちの猫、毎日お風呂に入れてあげてるのに全然なつかないんだけど…。
You know what, my cat doesn't take to me at all, even I bathe him every day....

入れるからだろ。
It's BECAUSE you bathe him.

Likewise,

いや、そりゃかたいことばかりは言えないがだ。
(lit. No, you know, it is that though (you) cannot always tell moralistic things.)
something like: No, of course I don't say you should be always prim and proper.